Problem following my intake manifold explosion!

Slacey · July 13, 2005, 18:55

As you may have read, last Sunday I had a freak explosion in the intake manifold which initially I thought had blown a hole in it, fortunately it just popped off the PCV hose.

Anyway, when I drove the car the following day, it seemed OK, maybe the odd hiccup but I put that down to paranioa. The following day I drove 20 miles to work and although it stuttered slightly on cold idle on the driveway, it was fine. Now, I had to use the car a lot that day to go see some clients, and as the day wore on the car started to stutter on occasion when under light acceleration and cruising speeds. This progressively got worse, with the stuttering happening pretty much in any condition other than idle and hard acceleration, which were fine. As the weather and car were really hot, I put it down to that.

So to today - I had to take the car for just a short journey of around 4 miles this morning, and it stuttered terribly. On cold start the idle was really lumpy, to the point of me pulling forward, dipping the clutch and the car dropping rpm's so low it nearly stalled. It then stuttered all the way to my destination; in all honesty I thought it was going to pack up before I got there. After it had sat for an hour or so, I left for home, and strangely the stuttering although still there wasn't as bad.

I have this afternoon cleaned the MAF (did this a week ago) and pulled ALL of the IC piping (which had a little oil in them) and cleaned then reclamped. I then took it to the petrol station (a few stutters) and filled up with my usual Optimax and then drove around for a while. The stuttering was a lot less, but still there.

Any ideas? The car frustratingly doesn't throw a CEL, so it's a pain to identify what could be the cause. The stutters are very slight, only for a split second but you feel the car dip, as though you had come off the throttle. There are no pops or bangs, or any strange noises for that matter. Is it related to my explosion (likely IMO) or complete coincidence? Either way I am getting proper pissed with the car these last few days s:evil: :evil: s:evil:

Anonymous · July 13, 2005, 18:58

Could possibly be contaminated fuel (possibly water) as you say it stutters less after a fresh tank?

Slacey · July 13, 2005, 19:06

Quote from: "Beastie"Could possibly be contaminated fuel (possibly water) as you say it stutters less after a fresh tank?

Possibly, but it was fine before the bang. There was around half a tank left when the problem started, I only filled up today so I could add a bottle of injector cleaner to see if that helped.

kanujunkie · July 13, 2005, 19:11

could the shockwave from the explosion have damaged the MAF sensor after all they are quite delicate, sound to me like an injector or air inlet problem and due to the explosion, more likely to be either sense or air control problem, any chance of borrowing someone elses MAF sensor Sean?

aaronjb · July 13, 2005, 20:02

Quote from: "kanujunkie"could the shockwave from the explosion have damaged the MAF sensor after all they are quite delicate

Indeed - and I've seen what happens when fuel vapour explodes in an intake manifold.. The sheet of flame nearly took my hand off! (Mind, that was a bent valve, so the cylinder filled with fuel & air and then ignited, straight back out the intake tract..)

Also - have you given that PCV hose a really good check, along with all the others? There's a chance it could be split, giving similar symptoms.. Or a crack in the inlet manifold s:? :? s:?

GSB · July 13, 2005, 20:18

Idle air control valve?

Its a small electronically controlled valve that bypasses the main throttle butterfly. On idle, the main throttle valve is completely closed, and the Idle control valve is opened and modulated by the ECU to control idle speed. It could be that yours has been damaged by the explosion, leaving it to stick in position. This would explain your rough idle anyway...

markiii · July 13, 2005, 20:31

Quote from: "GSB"Idle air control valve?

Its a small electronically controlled valve that bypasses the main throttle butterfly. On idle, the main throttle valve is completely closed, and the Idle control valve is opened and modulated by the ECU to control idle speed. It could be that yours has been damaged by the explosion, leaving it to stick in position. This would explain your rough idle anyway...

now that sounds likely to me

Anonymous · July 13, 2005, 20:52

presumably when the explosion occurred, at least 2 of the intake valves would have been open, could the explosion have damaged a plug?

kanujunkie · July 13, 2005, 21:01

Quote from: "spgreen"presumably when the explosion occurred, at least 2 of the intake valves would have been open, could the explosion have damaged a plug?

do you either the spark and injectors or an electrical plug?

Anonymous · July 14, 2005, 00:46

On WOT does it stutter or does it pull like it should?

Sounds alot like my O2 problem i had, but that would never be a result of your other problem, and in the end it would throw a CEL, but worth pulling them and checking them while your guessing on the culprit. s:x :x s:x

Slacey · July 14, 2005, 06:41

Checked the O2's - they look fine
Checked the MAF - looks fine
Checked the pipes and hoses - look fine
WOT - runs perfectly, no stuttering

Will tonight check the plugs, and yesterday I did actuall clean the IAC so I'm not convinced it's that - it doesn't explain the stuttering that happens when under normal driving conditions.
I'll report back as to how it runs today later...

Slacey · July 14, 2005, 08:54

Morning update - on cold start, it ran like sh*t again, and stuttered for a while until on the M54 (only a couple of miles from my house). After 5 minutes of 3500rpm cruising the stuttering stopped. And stayed stopped until I got to work s:? :? s:?

I did run an absolute crap load of carb / throttle cleaner last night and also tipped in a bottle of injector cleaner so maybe that has cleared it up?
I guess the test will be when I need to get home, and it will be under cold start conditions again. A couple of guys on SC suggested a small air leak, which sounds feasible so I will also recheck all of the hoses in the throttle body vicinity, particularly the PCV hose.

SteveJ · July 14, 2005, 09:27

One other thing to check is the throttle butterfly - given that it was closed when the explosion happened it may have been bent (unlikely) or knocked loose from its spindle (possible) and is fluttering when at low throttle settings.

Slacey · July 14, 2005, 09:33

Quote from: "SteveJ"One other thing to check is the throttle butterfly - given that it was closed when the explosion happened it may have been bent (unlikely) or knocked loose from its spindle (possible) and is fluttering when at low throttle settings.

Mark also suggested this, so I inspected it quickly last night while the IC piping was off. It looks fine as far as I can see, and felt normal when I manually moved it by pulling on the throttle cable. If the problem continues after further investigation I will reinspect this further. Anyone got a spare throttle body? s:lol: :lol: s:lol:

Jap GT300 · July 14, 2005, 09:36

I've had exactly the same problem with hoses not being clamped down correctly. Double check all the stock hoses around the throttle body.

re: IAC can you actually remove this to clean it? Is it in front of the TPS

Slacey · July 14, 2005, 09:47

You can remove the IAC as it bolts to the bottom of the throttle body, but it's a bit of a ballache as you have coolant running through it to let it know the engine temperature. If you take a look over at newcelica.org there is an article on how to remove and clean it.

Slacey · July 14, 2005, 19:00

Afternoon update - everything seems as sweet as normal. Between the copious amounts of carb cleaner and the bottle of injector cleaner it seems OK, hurrah! It was idling high at around 1100rpm, but I re-ran the ECU idle learn procedure and that has sorted itself out too.

However, I'm not counting my chickens just yet, I'll see how it goes for the next couple of days before declaring the problem fixed - I'll update again in due course.

kanujunkie · July 14, 2005, 19:01

fingers crossed, all's well that ends well

Anonymous · July 15, 2005, 05:46

I exchanged emails with JayHass today regarding the intake manifold spark and he's of the opinion that its a freakish Toyota problem.

Theory 1:
O2 sensor heater circuit is energized and both the intake and exhaust valves happen to be open on a vapor filled cylinder.

Theory 2:
A Pre-startup cleaning cycle is initiated on the fuel injector circuit.

They both sound "plausible" to me. I suppose a switch could be installed to prevent power from flowing on those circuits unless it was ON. And it would only BE on when one is seated in the cockpit with the pedal mashed not messing about with the radio, taillight or the odd bit of whatnot. s:D

s:D

Slacey, whats this IDLE relearn procedure? - Did you put in a PFC?

Slacey · July 15, 2005, 06:29

Quote from: "wts"Slacey, whats this IDLE relearn procedure? - Did you put in a PFC?

No; just a case of resetting the ECU then leaving the car to idle for 5 minutes with no electrical load, then 5 minutes with the aircon on.
One thing I have noticed is that when N/A an ECU reset never required this procedure (either that or I just got lucky on the couple of times I did it), whereas now I am FI and piggybacked if I don't run through the procedure I end up with the car idling at 1100rpm as mentioned
TBH I find the easiest way is to reset, run the car as normal and if it idles fine then great, if not then reset again while the engiine is hot and it learns a lot quicker as it is already up to temp.

Anonymous · July 15, 2005, 07:34

Quote from: "Slacey"
Quote from: "wts"Slacey, whats this IDLE relearn procedure? - Did you put in a PFC?
One thing I have noticed is that when N/A an ECU reset never required this procedure (either that or I just got lucky on the couple of times I did it), whereas now I am FI and piggybacked if I don't run through the procedure I end up with the car idling at 1100rpm .

Oh, OK. But something else is going on with your idle. MInes never idled that high after a battery disconnect. N.A. or F.I. Sounds like you have a mis-adjustd/bent throttle plate or a mis-configured IAC and the ECU is learning around it.

I just got mine out of the shop where the battery had been disconnected and the idle was fine. 650-750 w/o AC. 800-1100 with AC.

Slacey · July 15, 2005, 08:49

It has done this since the turbo went on, not just after the bang last week so I don't think it's the throttle plate or IAC - could be wrong though.

Anonymous · July 15, 2005, 09:12

Reset my ECU every couple of months or so and also never needed to do anything but drive it. Yours does seem a strange one Sean, but aslong as it's working no need to worry.

Has anyone ever heard of this explosion in the intake ever happening before (except Jared) NA or FI ?I'm sure i haven't, seems like it's just a unlucky coincidence in such a short space of time.

Anonymous · July 15, 2005, 09:19

Something possibly related, on VAG engines, is the regular 'need' to do a 'throttle body alignment'; turn on the ignition, but don't start, and leave it for >5 minutes. After a minute or so, the ECU begins a 'calibration' sequence on the throttle body, to match it to the (admittedly drive-by-wire) pedal position - you can actually hear it whirring and clicking away.

Is something similar worth trying/likely to have any effect?

Slacey · July 15, 2005, 09:27

It could be worth a try Phil, although the method I mentioned works for me every time. As a quick update the car strated fine, idles a little unevenly but once off the driveway was fine. This would seem to imply that the cleaning process I went through has pretty much sorted the problem rather than it being something more sinister or an air leak. Mark has suggested I run a can of 10K Boost through the system, this seems like a good idea as the car now has three years worth of coke and crap in it. Any thoughts on this, experiences good or bad?