NEWBIE needs help, throttle holds back

[andyhull]

Hi guys n gals
Great forum btw
ok, I have a roadster 2000 plate, recently purchased. I have an issue with the the throttle, that when I hit the accelorator the revs drop off, and will increase if i ease off the gas and accelorate slower.
It smells as if its running rich too so not 100% sure as to what the reason could be. I have seen similar things on the forum, but these were idleing / tick over issues, which this is not.
The same thing happens when I change gear, again it dies a bit until i ease off and slowly accelorate
It is now becoming dangerous, because if I dont have the revs up enough at a junction the car will stall.
The ecu has shown several faults, from pre / post cat sensors to maf, and had them all reset. They have not come back as of yet, but not done many miles.
It did have a misfire one, but that was when i first bought it, and since reset it has not occured again.

DONE UP TO NOW
checked for air leaks = none
checked plugs sparking = ok
ran injection cleaner through
checked oil filter = ok
Cleaned maf sensor
I did notice though, that the air intake elbow that connects to the bodywork one, was not fitted inside correctly, so I managed to fit my fat hands inside the bay and tuck it in, but its not sealed in any way.
I also unplugged the maf sensor and then tried the revs, and the holding back it was doing before vanished and it reved up lovely. However at the top end of the revs it started acting up, making a weird woo woo woo sound as the revs were kept on ( hope you can grasp that bit )

I have an obd2 reader coming in the nxt cpl of days ( cheap as chips now  :-) :-) :-)  ) and can then list the full codes as and when they pop up.
Again, I have limited knowledge round car engines, so plz plz be patient with me.
Any help would be greatly appreciated
Andy

[redarrow]

Where all waiting for the code reader first.

I hope you doing every think from
The how to  when cleaning the maf  and ect.

Have you cleaned the ivac and throttle properly
While waiting for the code reader.

What you said can be a lot of symtoms

Example only

Sticky throttle
Maf broke gone
Iac needs cleaning ( this hangs of the throttle
Any pipe holes
Are the side insert pipes ok
Is the air filter ok
Is the accretion cord ok
Ignigton leeds , coil packs , sparks ok

All i can say and you cheek

Regard john

The code reader will help a lot but also
You cleaning the bits you no about and do it properly
And replace properly will encrease your chances get it done
If you need help on things there youtube on the net
Anythink that gone to far to get working
There the scrap yard and ebay to replace them.

[andyhull]

Thanks for your reply mate, but as I said I am very new to this and not very good around engines lol
I will have a go at all those things, but can you point me in the direction of the ivac and throttle plz, any links for pics etc would be great

[spit]

Hi Andy. Welcome to the ROC   s8) s8)  

I'll fish out some pics from other threads for you in a moment and post them here.

It  looks like you're working through stuff in a sensible fashion, so don't underplay your ability around engines   s:D s:D  Most of us are learning by sticking our heads in and getting grubby! And making plenty of mistakes along the way   s:wink: :wink: s:wink:  

Like you, I'd also be suspicious towards MAF and vacuum leaks as a first port of call. From your brief desription it certainly seems to be pointing towards a fuel/air mix drama.

The IVAC on our '2 has a habit of gumming up which can affect idle fuel/air control and lead to a slight stumble when you open the throttle, although it sounds like you're experiencing something a little more harsh?

The throttle position sensor is something else to add to your look-list. Fuelling will take the throttle position into account and the TPS is a fairly simple potentiometer that provides this info in the form of a reference voltage to the ECU. A dirty pot track can cause this voltage to spike a bit, particularly at the low throttle end where all the crud tends to get dragged over to. The result can be portions of throttle where the ECU is misinformed or rendered clueless.

I'd also be inclined to look at O2 sensors and injectors again as they're instrumental in getting the car at the optimum tune for smooth pick up. For info (if your misfire ever returns), funky injectors can bring about a misfire code as well as the obvious coil pack/spark system.

Thats most of the small stuff covered. Bigger stuff could include cruddy air filter, exhaust blockages/leaks and some other nasties that you'll hopefully not have to get into   s:D s:D

[spit]

Here y'go, stolen from an unrelated thread so ignore the labels!



Follow the intake pipe from the MAF round to the back of the engine and you'll see the throttle body. With pipe and battery out its easy to get to,

TPS connection is at 3 o'clock in the picture, IAC connection at 7 o'clock.

You can play around with this stuff on the car. If you opt to remove the Throttle body (2 12mm bolts + 2 12mm nuts - 3 of which are visible here), you'll need to clamp off the two small hoses (at 5 o'clock) as they're coolant feed and return for the unit. Throttle cable is attached at 10 o'clock via the bracket (12mm open spanner) and wheel (release the cable nipple!).

To get to the IAC spindle you'll need a very rare 5-point torx to remove the plastic cover. If you can't find one and need to borrow, give me a shout.

[andyhull]

WOW thanks spit, awesome job mate
I gotta say I was laughing my head off reading all of that lol cos I truly am clueless !! The picture and instructions are a god send mate, and much appreciated.
I read in some previous post that the IAC and throttle body can be cleaned using carb cleaner !!! Can you confirm this  and whats the best way to start a clean with it all in situe ( if possible that is )
Love my MR2, wanted one for many a year, went shopping with wife for some new curtains and saw it advertised lmao,,, had to have it. Sod the curtains lmao.  Just hope I have not bought a bag of bones  s:-( :-( s:-(

[spit]

There's no official method for using carb cleaner on the TB. Chances are we all do it differently! Others may have their own tips and will probably be along shortly to chip in......

I'd opt to take the IAC apart and clean it out separately - working on the car there's no assurance that you've nailed it or got the cleaner to penetrate the rather delicate valve. That said, carb cleaner in situ can go a long way towards cleaning stuff up. Depends on how OCD you want to be with it.

If you go for stripping the IAC, be warned that the rubber seal that separates the coolant and air channels is a diabolical fit and needs to be reassembled with great care and/or lateral thinking!

Introducing cleaner while the engine is idling is also do-able, although you'll need to grab the throttle lever and play the revs or it'll stall. Breather pipe (labelled in that pic) is a reasonable place to introduce the spray as you can retain a decent seal on the system and avoid upsetting MAF readings. Don't do this while standing near the exhaust if you value clean trousers   s:D s:D

Of course this may not be your issue, and components like the throttle sensor will still need to be given some individual TLC.... but hopefully it'll prove handy as you work through and cross things off your list.

[andyhull]

Thanks for that mate, I will start first thing in the morning, but I also want to see the codes for myself. I have serious doubt about some garages giving the whole truth etc, so once my little device arrives i can see for myself.
Slightly off topic, the bloody 3rd brake light isnt working now lol, changed all bulbs and nothing. Any tips on using a mega ?

[andyhull]

Hi guys
I have another question  s:-( :-( s:-(  
ok when i unplug the MAF the cars intial problem of holding back on first throttle seems to go away, and revs nicely up to 3000. When it reaches 3000 it wont go any further and starts its up and down motion of revs.
The question is, if the MAF is unplugged on other roadsters, does the same thing happen ? and also ( if it is standard ) could it mean the MAF is the cause of the holding back on revs ? or is it just not that easy.
I appear to have no air leaks and all pipes look ok. The fault reader will be here tomorrow but will show MAF due to me unplugging it etc. I will run the car for a bit and then see what comes up on the diagnostics.
I tried to get the air filter top off to check the filter ( allegedly has been done by garage, but who knows ) but can i hell figure out how those clips come off !!! They are the ones that face you when looking in the engine bay ?
thanks guys, and plz be patient with me lol

[spit]

Looks like its just you and me Andy   s:D s:D  

The question is, if the MAF is unplugged on other roadsters, does the same thing happen ? and also ( if it is standard ) could it mean the MAF is the cause of the holding back on revs ? or is it just not that easy.

Temporarily unplugging sensors and getting a different response from the engine (or no change at all) can be a handy diagnostic trick. Its not always an absolute confirmation of the problem but it adds to the jigsaw.

In your case, I'm afraid I just don't know. My experience with (otherwise OK) 2's is that they're lumpy as hell with an unreliable airflow reading or with the MAF unplugged. That said, I've got an old Mazda with absolutely identical symptoms to your '2 and I get the same smoother low rev with the MAF unplugged, even though the MAF is apparently doing its thing and reading fine. Pretty stumped with it   s:? :? s:?  Next port of call is the O2 sensor followed by the scrap yard   s:lol: :lol: s:lol:  

Several members have spare MAFs they'd be willing to loan for a temporary swap-out - thats a quick and cheap way of knowing for sure whether yours is a lemon. Its probably the route I'd take - ROC members are generally a friendly and helpful bunch!

Let us know what codes are appearing on your new reader and we can continue to build up the picture from there.

[andyhull]

Thanks for that spit
Ok the codes before reset were :-
P0100 ( expected because i unplugged the MAF )
P0110
P0141
After reset all have cleared, I even took the car for a short spin , but the slugish pick up on aceleration is still there ?
I will test it again later today, after a longer run
Bloody thing is doing my head in lol   I even had a tour round the area looking for MR2,s parked up etc to see if i could try their MAF lol  but found none
If anyone is willing to borrow me one for a test, I would be extremely greatful. I am in east yorks, hull area
thanks

[Anonymous]

Hey Andy!

It looks like we have a very similiar problem, although I am not getting a check engine light.  Also my shifting problems are only noticable when going into 1st gear from a stop and accelerating quickly.  I posted a very similiar issue on spyderchat.com the same day you did and I also have a newly purchased 2000 spyder!  Here's the link: http://spyderchat.com/forums/showthread.php?57853-Throttle-Lag

I will keep watching this forum incase you have any success diagnosing the problem.  When I get some time in the next week or two I will be pulling the throttle body.  I am also very new to engine work so it should be interesting!  I plan to clean the TB and the IACV, although I'm hesitant to completely dissect the IACV.  This process is shown in detail here:  http://www.mr2spyder.net/spyderweb/index.php?/topic/2951-cleaning-the-iac-valve/  I will also do some tests on the Throttle Position Sensor (TPS) to see if it is functioning correctly.

I'm hoping that you can get your hands on a MAF Sensor to see if that's the problem as I do not have access to an extra one either.  I hope we figure this out soon!

Andrew

[andyhull]

I read on your post that you dont have throttle lag when in neutral ? is this right ?  I have the problem even in neutral, step on the gas and it holds back,, ease off the gas and it will pick up. Its a pain in the rear when coming to junctions etc as I dare not try to nip out in a que of traffic in case it stalls
When i'm running through the gears it does a similar thing if I try and accelerate to fast ( foot down ) but if i ease onto the gas gently it runs fine.
I have had it suggested that the post cat sensor COULD be causing an issue with the ecu, so I am going to remove this and try to clean it, just to see if anything changes
Its gonna be trial and error, but the TB sounds a good place to try too. Thing is I am useless with stuff like this, and its a tight squeeze lol. Plus once its off I would probably  scock cock scock  it all up trying to get it together again  s:-( :-( s:-(
I will keep posting any efforts in here, and if anyone else has any suggestions that would be great

Just remembered that when I cleaned the MAF sensor, I did not reset the ECU. Should I have done this ? and if so can this still be the cause ?  questions questions eh, sorry guys

[Anonymous]

I agree, you are experiencing the problem to a more severe extent.  I only notice it when I slam on the gas going from a stop.  It might happen for me if I slammed on the gas in neutral but I will spare the car of this torture.  Between gears I'm not noticing a problem, but again maybe I would if I drove more aggressively...  

I too am concerned about removing the throttle body and IACV.  I have never done it before on any car and I've been learning a lot as I go.  I will almost certainly screw something up, but I will learn from my mistakes and hopefully they will not be too costly...  Thankfully, there is a ton of useful information on sites like this!  I will need to take it slow and put aside a large block of time for the project.  Hopefully next week!

From what I've read, you should reset the ECU after cleaning the MAF.  I disconnected the battery, but if you're concerned about your radio presets you can pull the ECU fuse.  This will give the ECU an oportunity to relearn based on the cleaner sensor.  Hopefully cleaning the post-cat sensor will help.  Thanks for posting all the details of your problem and what you are trying!  It is still possible we have a problem in the same part of the car.

[andyhull]

Ohhh without a doubt its related, but we will get there
Today I did the following :-
Cleaned air filter ( not needed really but did it )
Checked for air leaks using a smoker
Sprayed carb cleaner in the breather pipe while on idle ( the crap that came out lol )
Changed all spark plugs
Reset ECU , removed batt for 20 mins
Still having the issue but I am not sure the carb cleaner has cleaned the sensors, so my next job is to tackle the TB and IACV. Like you said, I guess we will learn the hard way  :-) :-) :-)
I have a sneaky feeling its the IACV but what do I know lol  Only way is to go through it all bit by bit, and a dam good clean and service of all these bits will go along way anyway.
If all else fails I am going to bite the bullet and order a new MAF and o2 sensor, and if it still persists I can at least re sell them both as new ( ish )
Ohh well, back to the grind stone tomorrow, even though footy is on  s:-( :-( s:-(   Hey I,m learning slowly, proud of my work today lmao

[andyhull]

I am happy to report that I have now resolved the issue of Throttle holding back from idle and through the gears.
After much research through this brill forum, and speaking to a few fantastic members, I eventually opted to replace the MAF.
Well bugger me, a cheap £35 ebay MAF has stopped the lot   s:D s:D   It now revs as it should and has no holding back at all.

I went for the MAF exchange due to the P0171 / 174 codes both coming on together, as the likely hood of both going together is remote. I had checked all the usual suspects, air filter, air intake, throttle body, plugs, and fuel pressure, which all seemed ok.
So it just shows what codes this MAF can throw up when it fails, and what it does to the car running !!!

Thanks guys its much apreciated   s:D s:D    s:D s:D    I now have to change the post cat sensor only, as this was being thrown up all the time, and still is.
Rockclimber, I know you have very similar problems mate, bite the bullet for £35 and try the MAF   s:wink: :wink: s:wink:

[spit]

Good work Andy   s:bounce: :bounce: s:bounce:  Now that you've taken the plunge with fettling, you're on your way to having some great fun with the '2.

Once you've got those tyres sorted out, let's get you along to a meet.

Go well.
Ste

[redarrow]

Andy did you get a cheap maf from ebay but new?
Regards john

[andyhull]

Yes mate, it was new and cost £35

[redarrow]

Can i have a link to the ppl you used as you got a good batch cheers mate.

[andyhull]

I was going to post the link before but thought it may not have been allowed. It was £37.99 not £35
Here is the link
 m http://www.ebay.co.uk/itm/151022141473? ... 1439.l2649 m

[mrivett]

Hi. I've now got the same problem, but when the throttle stalls the heat gauge goes down to zero for a few seconds and then rights itself and the stalling goes away. Did 8 miles this morning and it did it 4 times. Engine seemed really hot when I stopped. even the coolant was hot. I have cleaned MAF and carburettor.  Oil and water ok.  Anyone any ideas?  :-) :-) :-)

[Jon_G]

Hi. I've now got the same problem, but when the throttle stalls the heat gauge goes down to zero for a few seconds and then rights itself and the stalling goes away. Did 8 miles this morning and it did it 4 times. Engine seemed really hot when I stopped. even the coolant was hot. I have cleaned MAF and carburettor.  Oil and water ok.  Anyone any ideas?  :-) :-) :-)

The heat gauge dropping like you describe suggests an electrical problem. Check fuses and connections.

[mrivett]

Think I might have solved the problem. There was an unplugged pipe  :-) :-) :-)

Before:



And after:



I'll give it a test run later when I go to work and let you know.

[andyhull]

Thats weird, because when I first started diagnosing my fault, I also found the same pipe off !! It was not the cure for mine, but I rekon it could be for yours   s:) s:)