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Old 08-06-2011, 07:50 PM   #1
olopezm
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Surging when in gear

Hello guys,

I would like to give a background of the situation first:

The car was stored for a few months and when I finally went to get it ready I started the engine and it hesitated for a few seconds (nearly stalled, the charging system light started blinking as the engine tried to keep turning over) then everything went back to normal. I can tell it only happened once every cold start in the morning, after that engine would work OK for the rest of the day.

Platinum spark plugs had less than 1k miles on them but I decided to inspect them for peace of mind; they were fouled and had a fuel smell. I noticed a strong smell coming from the exhaust with cold engine and since it happened only during the open loop mode I decided to remove the ECT sensor to inspect it, it seemed fine but after taking a close look at it I found a small crack at the plastic connector base, when I wiggled it a little it just came apart so I replaced it with a new one expecting that would also get rid of the hesitation but it didn't.

I also gave the throttle body some cleaning with coat safe cleaner, after that the engine just kept stalling and wouldn't idle without holding the throttle open, which I did for a few minutes. LOTS of smoke came out from the exhaust and I attributed it to the cleaner. When it finally idled by itself I thought I was done but as soon as I shifted in gear it started to misfire so badly that I decided to just leave it alone...

So fast forward to last monday; I started the engine and was the same so I took one of the plugs out and was coated with lots of carbon and had some fuel on it. I decided to replace them with new ones and since someone mentioned the hesitation could be due to a bad IAC I decided to get a new one too.

After I came back home from the store with new plugs and IAC I installed them and started the engine, it seemed to be fine but as soon as I put it into gear it kinda hesitated and started to surge while idling in gear, when I shifted back to neutral or parking the RPM's would go up a little and go back down to normal I got sick of it and stopped working on it for that day.

When I got inside I found out the guy gave me Autolites 765 (copper core) which are one step hotter than original plugs. Would this cause any problem?

I was busy with my relatives during the past days but within the next days I will be replacing the IAC with the old one again to see if it makes any difference.

Another friend told me I might have carbon deposits in the cylinders and that would also cause the surging. Any ideas about it?.

Thanks in advance for any help,

Oscar.

PS. I've uploaded a picture of what the plugs look liked the first time I took them out.

EDIT: I forgot to say the car has 186492 miles on it
Attached Images
File Type: jpg IMG00194-20110728-1049.jpg (38.2 KB, 8 views)
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Old 08-09-2011, 06:17 PM   #2
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Re: Surging when in gear

Your stalling seemed to be related to IAC. It's a common failure and sounds like you correctly fixed the issue. I would leave the new IAC on.

If your spark plugs are carboned up, you will have carbon deposits in your cylinders. Get a can of Seafoam and use the ENTIRE can through your PCV or brake booster line. This will clean out the intake manifold, plenum, valves, and the cylinders themselves of carbon. Lots of white smoke will be visible and this is normal. Do it in a ventilated area.

The one step hotter plugs will actually burn off deposits better than the stock heat range. The down side is you might experience some knocking/pinging due to the excess heat buildup. You usually won't get it unless you really put it under a lot of load, though.

The fuel smell when the engine is cold is normal. The engine computer runs rich in open loop mode to ensure it will not get lean and cause damage.

What's the condition of the coils and wires? The miss might be occuring because of a weak spark which would leave unburned fuel in one or more cylinders.
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Old 08-09-2011, 08:16 PM   #3
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Re: Surging when in gear

Thanks man, it's been a long time...

I have BAD news, one of the bolts holding the IAC in place broke while I was trying to swap the IACs. Now I have to deal with this thing...

Tried used vice grips to get it out with no success
Tried making a slot on the top of it to use a screw driver, no success
Tried using an easy out and the damn thing broke, no I need to deal with even harder material (35 bucks gone to the garbage...)

It's a PITA to reach that place, I was thinking about getting a set of titanium drill bits but I'm still deciding to either do it in-place or removing the intake manifold to have more space, I think both options suck!

I'm guessing I'll need new intake gaskets or can I reuse the old ones? They don't have many miles on them since I replaced the under intake hose.

Any other ideas on getting that damn thing out?

About your ideas:

- Seafoam is not available here, so no luck there...
- I was thinking the same about the pinging but, in case it happens, switching to a higher octane should get rid of it, isn't it?
- Fuel smell seems to be very different since the last time, right now I can say it's a normal smell, before that my eyes would burn while taking it out from the garage.
- Haven't tested the coils, but I might. Wires have less than 1k miles on them, were replaced a year ago when I did the full tune up. Still I decided to take them out, clean them along with the connections at the coils. Unfortunately I couldn't start the engine because of the broken bolt so I still don't know if it made any difference. But I'm confident it will!

Thanks in advance,

Oscar.
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Last edited by olopezm; 08-09-2011 at 09:12 PM.
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Old 08-22-2011, 07:31 PM   #4
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Re: Surging when in gear

Hello again guys!

It's been almost two weeks since the last time and LOTS of things have been going on.

I had to remove the intake manifold in order to drill out a broken IAC mounting bolt, it wasn't that bad but definitely wasn't expecting it to happen and being on a tight budget makes matters worse. Anyway i'll list what I have done so far, which hasn't improved anything, the problem persists.

- Installed new intake manifold gaskets and properly torqued everything.
- Installed a new IAC and new spark plugs to no avail.
- Installed a new ECT since the other one was broken, no change.
- Checked for any vacuum leaks listening with a hose and found nothing, I hooked up my scanner to confirm this and found the LTFT levels at 0, STFT readings range from 0 to -3 %. So NO vacuum leaks.
- Cleaned throttle body, no change.
- Cleaned EVR filter and measured resistance across it's terminals, got 34 ohms which AFAIK should be OK.
- Pulled vacuum with my mouth on the EGR valve and holds vacuum, I can hear a popping noise which indicates the diaphragm is OK and moving inside.
- Tested DPFE sensor, has proper 5v feed and signal return varies from 0.49 to 4.9 volts when pulling vacuum on the REF hose.
- Cleaned/inspected IAT and measured resistance accross it's terminals, it's OK. I looked at the IAT PID and reading is about the same as the reading in the EATC module at ambient temperature. IAT was 27, EATC was 28 (ºC).
- MAF PID is ~6 g/s at idle.

So far those are the things I'm sure are OK.

The following items I'm not sure, I tried to find the specifications for the coils but couldn't find them anywhere and the computer which has the service manual installed in it has been acting up again so I currently don't have access to it. Any thoughts about these?

- Measured resistance at (4) primary ignition coils and got 0.8 ohms. On the secondary coils I got:
Passenger side Top 12.48Kohms Bottom 14.51Kohms
Driver side Top 14.26Kohms Bottom 14.16Kohms
- Checked O2 sensors readings and got:
O2S11 - 0.280v
O2S12 - 0.100v
O2S21 - 0.755v
O2S22 - 0.075v

Here's where I found a weird thing, after shutting engine off the 4 readings won't drop to 0, will range between 0.075 and 0.085.

I was thinking the O2 sensors shouldn't be a problem when cold, just like the MAF but at this point I am no longer sure

Also I'm having a slight misfiring at idle, that's what makes me think the coils could be bad (originals) but I don't know if they could cause my original problem (cold start hesitation only ONCE every morning).

Thanks in advance for any help, this is starting to drive me nuts!

Oscar.

EDIT: One more thing, should I leave the new IAC installed (since it made no difference) or put the old one instead, I tested resistance and both show the same reading.
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Old 08-23-2011, 03:55 PM   #5
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Problem seems to have been finally solved

It seems I managed to fix the problem.

When I first took out the thermostat to remove the intake manifold it was broken at one of the legs between the round part and the spring assembly in such way that coolant was flowing all the time. I didn't think this could have been causing such problem and thinking the guy who fixed the under intake heater hose some time ago damaged it I just tossed it away. As a note I must say the car never showed any overheating symptoms.

When I completed the installation of the manifold and the rest of components I decided it would be a good idea to flush the cooling system and put an additive to remove sediments, corrosion and stuff from it so I decided to cut the old thermostat and reuse the old gasket, installed it and started with the flushing procedure following the instructions from the additive and after that decided to follow Dereck's flushing procedure too. I left the car like that and didn't install the new thermostat.

Fast forward to yesterday, when I started the car it seemed to be fine but after a few seconds it immediately started hesitating again, just like before. That's when I decided to test all of the above components and rechecked all connections and hoses. Needless to say I had no success. At that moment I decided to install the new T-stat (motorad) but found out the gasket wouldn't fit in place. I went to the place I bought it from and the guy said that was the only they had with a gasket. After arguing for some time the store finally agreed to return my money. I went to the dealer and got a new thermostat and gasket as separate items.

Today I did another cooling system flush before installing the new thermostat and checked all sensors again. I installed it along with the new gasket, filled the system, did a final check around the engine and when I was satisfied I fired it up. VOILA! It didn't hesitated/stumbled at all. Idled fine and seemed to be more responsive. Left the car idling until the temp reached the normal mark; did a final check on the coolant level and it drop down only a little I refilled to proper level and shutted engine off. For peace of mind I started the car again and was idling great.

So all this problem was caused by a $15 item, did lots of work before finding out such thing. Needless to say this is the first time I get such behavior from a car running without a thermostat . I learned something new, from now and on that will be one of the first items to inspect.

Even when it should have been a cheap fix, after replacing all those items, I'm happy that I did all that work because now I know the engine (at 187500 miles) is in good condition and everything was done according to specs, unlike all of the mechanics I know around here who never use torque wrench... As an example the guy who fixed the under intake heater hose reused the old gaskets and still charged for a new set . I'm also glad I got my cheap scanner, without it this could have been a painful task.

I really hope this information helps somebody else, I'll be happy to know I helped somebody to save time and MONEY before attempting all those repairs.

If anybody has any questions or comments feel free to post here, send me a PM or contact me via e-mail.

In case I get the same problem again I will surely post it here and keep updated.

Greetings from Mexico!

Oscar.
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Old 10-12-2011, 10:22 PM   #6
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Re: Problem seems to have been finally solved

Oscar,
Being pretty familiar w/ a '95 TC, (mine has 202K on her) did you pull the elbow behind the throttle body, (4 ten mm bolts) and clean out the horseshoe shaped passage way that the EGR dumps into ? A while ago mine was level full of hard carbon build up. I chipped it out w/ MEK and a small screw diver.
Also when you look @ the engine from the front of the car, there is a big black plastic tube that enters the elbow on the drivers side and it plugs into the back of the engine way in the back, down low. If this is disconnected @ the engine, it will cause surging and will eventually stall down the road. But it will sit there and idle like a champ.
Just som things to check.
Mike in Colorado
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Old 10-13-2011, 07:51 PM   #7
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Re: Surging when in gear

Hi Mike!

Thanks for your suggestions both are valid; yeah both things were ok.

I forgot to update this post but in the end it turned out to be the fouled spark plugs. After that the car would start bucking under load, the more load harder the bucking. It turned out to be bad wires. I got a set but haven't installed them.

At the moment the car is parked after the rear driver side wheel nearly came off after a 60 mile drive on the highway. I'm thankful it happened after I arrived to town and was driving at very low speed because of traffic. I will eventually deal with it; I just don't feel like it at the moment.

Oscar.
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