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Idle is surging all over the place and now occasionally dies. Seems to be about 500 - 1000rpm.
- Air cleaner clean; preheat valve fixed in permanent fresh air
- IAC is clear as cleaned 5K miles ago.
- Cleaned out throttle body last night (made problem worse). Audible click of TPS can be heard.
Attempted to set base idle (via black knob) with IAC hose plugged. Really didn't affect idle.
Other oddities. Car now seems to ping at boost - this is running usual tank of 90 octane 10% ethanol blend. Maybe a bad tank of gas??
More history: Recent T-belt change although it idled OK immediately after. The only strange part of the t-belt job was the cam gear wobbled when I took it off—IE the roll pin was bent over a bit. I did straighten and insert but wondering if previous owner had timing adj to compensate.
Apologies in advance as I realize I'm all over the place here. Need to step back a bit. Any insight appreciated at this point.
--
Norm Cook; Vancouver BC; 1989 745T 212,000KM
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posted by
someone claiming to be fixit 2003
on
Sat Jan 14 10:48 CST 2006 [ RELATED]
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Were you able to check the timing w/ a strobe light? I believe it should be about 10-12 deg BTDC for the #1 plug at idle. Also check for a leaking fuel reg vacuum line. Could be dumping gas into the intake manifold. If you have a Mitsubishi turbo check the end of the hard plastic tube going across the valve cover. Mine split where it attached to the flame trap. Hard to see unless you remove the tube.
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Hi fixit, thanks for the replies.
I haven't checked the timing although it's an inconsistent surge at idle transforming into a miss at higher rpm.
As per my reply to Big Harry below, I unplugged the AMM and it ran better so common Brickboard Wisdom tells me it may be at fault.
I'm curious to know how/why these units fail when there's no obvious problems—IE stuck air flap. Maybe at one time the air flap was stuck on ... who knows?
--
Norm Cook; Vancouver BC; 1989 745T 210,000KM
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Don't be too quick to diagnose AMM. I think most often with a bad AMM, the car won't run at all until you unplug the AMM to achieve the "limp home" mode. Did you check out the flywheel (rpm) sensor? If that goes, as commonly happens, it can cause symptoms as you describe. And did you check your distributor? Does your car have one of the Hall sensors which typically crap out and cause similar issues? Cracked distibutor cap maybe? Did you pull a plug; look at anti-freeze; look at oil? Check that out. Could be a head gasket. So many problems -- so little time.
Allen
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I am confused.
No flywheel sensor but it does have the hall effect and it was replaced around '99 (I think) so I'm not suspecting.
Took distributor cap off a few nights ago and it was fine.
Antifreeze is OK but yet to check oil. I don't think it's headgasket since this was also done in '97 and it would be a rough idle (I think). This is more of an inconsistent surge.
So little time is right. This has been going on since last Wed evening .. good thing all of us fit into the '84 Honda Accord.
I think the FAQ said if it car runs better it probably is the AMM. Thanks for your help.
--
Norm Cook; Vancouver BC; 1989 745T 210,000KM
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The head gasket could be the culprit. A friend pulled a 92 944T in my drive, and it started running like Norm is discribing. I remember unplugging the AMM and it smoothed out. I heard later that he had to have a new head gasket installed. I've torn down 4 B230FT engines in the past year and found every one had a head gasket problem from completely blown to weepage between the cylinders. The mileage on those engines ranged from 149k to 200k.
Regards,
--
Will Dallas, www.willdallas.us, www.willdallas.org, www.willdallas.com 86 245 DL 222K miles, 93 940 260K miles, 88 765 GLE 152K miles, 86 244 DL 200K Miles
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Hi Norm,
You can test the IAC by removing the hose at the manifold and plugging the manifold port with your finger. Let just enough air in for the engine to idle. If it will without surging the IAC is bad. I had two in a row with oil fouled brushes.
Regards,
--
Will Dallas, www.willdallas.us, www.willdallas.org, www.willdallas.com 86 245 DL 205K miles, 93 940 250K miles, 88 765 GLE 149K miles, 86 244 DL 200K Miles
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Will;
I've disconnected the IAC hose from turbo intake and it's pulling a heap of vacuum at idle so I assume it's working. I'll try what you suggest though.
Something has changed all of the sudden though because now the exhaust has a different smell - and I *think* it's rich. It's hard to tell because a rich smelling carbureuted car—say from the 60's—is a more fuel smell than FI cars with O2 sensors/cats.
It's hard to check for vacuum leaks though when the idle is loping. A few things I'd like to check:
- AMM
- Timing
The clues I have are this: pinging on boost, and oddball exhaust smell + loping idle.
I checked the timing marks last night though and 0 degrees on crank aligns with cam notch.
--
Norm Cook; Vancouver BC; 1989 745T 212,000KM
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Hi Norm,
If the smell is like rotten eggs it is probably running rich. I've purposely advanced the timing until the engine pinged under load without having the engine "hunt" at idle (15-17degrees BDC). It could be the knock sensor. I had one on the 940 go bad and it definitely affected the idle. There is a section in the FAQs about those. Also, if the coolant temp sensor is bad, the car will run rich thinking it is still cold (or vice versa). That unit needs to be removed to check it unless you have real skinny arms and small hands.
I wish you well with it. After over a year of puttering with the 88 765, I took it off the road. The 245 and 944 are much more reliable and get about 7-8 mpg over the turbo.
Regards,
--
Will Dallas, www.willdallas.us, www.willdallas.org, www.willdallas.com 86 245 DL 205K miles, 93 940 250K miles, 88 765 GLE 149K miles, 86 244 DL 200K Miles
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Now that I've had more time to look at this, this surge/hesitation is not at idle only.
Having said that, I'm not sure where to go next..?
ECT was replaced back in '97 so I'm doubtful it's failed. AMM? I don't know about that either as I have my airbox stuff to cold.
It does have the rotten egg smell though so it is rich.
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Norm Cook; Vancouver BC; 1989 745T 210,000KM
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Well, this is certainly a head scatcher. I think that you can eliminate the IAC because it is not an idle only occurence. The ECT is still suspect. I was given the 86 244 because of the black smoke pouring from the tailpipe. The ECT on that one had been checked but turned out to be the culprit. Another thing to look at is a manifold leak. If the engine will rev smoothly but is uneven at any static rpm then an air leak is indicated. I would spray a little Dexron tranny oil around the flange and the injectors then check for smoke. When did you change the injector seals last? I have some spare injectors if you find that they are the problem.
I don't know about the AMM, but I have a spare one of those also.
Regards,
--
Will Dallas, www.willdallas.us, www.willdallas.org, www.willdallas.com 86 245 DL 205K miles, 93 940 250K miles, 88 765 GLE 149K miles, 86 244 DL 200K Miles
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I ran WD-40 around the injectors + top of intake manifold gasket and didn't notice any rpm change.
I did unplug the AMM and the car runs better—it still stumbles a bit but not so much. I guess that's not a good sign for the AMM.
That could be why it was pinging on boost..? If the AMM has failed it wouldn't be able to send proper air info to computer for stoich.
0 280 212 007. Maybe I can get a spare around my area to test. How much you want for yours?
--
Norm Cook; Vancouver BC; 1989 745T 210,000KM
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Send me the address and I will one out for the postage, C.O.D.
Regards,
--
Will Dallas, www.willdallas.us, www.willdallas.org, www.willdallas.com 86 245 DL 205K miles, 93 940 250K miles, 88 765 GLE 149K miles, 86 244 DL 200K Miles
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posted by
someone claiming to be fixit 2003
on
Thu Jan 12 10:01 CST 2006 [ RELATED]
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Try testing your IAC valve. It may be clean but not rotating properly. If the turbo bypass valve is not working excess turbo pressure will be forced through the IAC when the throttle is closed. This sometimes pushes oil into the IAC and gums up the brushes st the valve doesn't rotate properly. You may see oil seeping out of the connector plug on the end of the IAC.
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