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Author Topic: Rough idle + gas in tailpipe  (Read 1988 times)

LlamaLover

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    • 91 Capri XR2
Rough idle + gas in tailpipe
« on: July 20, 2020, 07:08:21 PM »

Hi guys, I picked up my 91 XR2 5 speed a month or two ago and have been getting it all fixed up, as one does.
One day it drove perfect and I took it to be inspected, next day it decides to throw a tantrum.

It started up with a little gas, but idled super rough. Kept stalling out. Took it around the block, smells of gas, fumes pouring out the back. Cut out every time I hit the clutch.
Got back and checked it out, straight gas was coming out of the tailpipe.

Today, it started up and idled perfectly, but still has gas coming out of the tailpipe.

Stalking the forum, it looks like it could be the ECU, a sensor (presumably the O2 sensor), or the ignition module.

Does that sound like an accurate assessment? Did anything in my situation point towards one issue or another to you guys? Going to delve into the manual once again tonight and play with it after work tomorrow.

Thanks for any help! I appreciate the wealth of knowledge this forum has offered, definitely has made this car adventure quite a bit smoother.
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Rocketman

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    • 91 BPT AWD Capri & 1991 XR2
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Re: Rough idle + gas in tailpipe
« Reply #1 on: July 20, 2020, 07:27:50 PM »

Good to have you here, happy to hear the forum is still helpful to some folks.

First I'd pull the codes, to see if the ECU thinks there's an issue. It's easy, jumper the test terminal under the hood and flick the key on to RUN, then count the CEL flashes.

I've heard of the ECU failing, one of the injector channels farts out and opens two of the injectors all the time. You can check to see if all the injectors are firing, using a stick up against your thumb against your ear to listen for it, or a noid light.
The ECU is in a spot where the heater core or AC can leak onto it, most have some rust on the covers. If it's invaded the circuit board it might cause some issues. You could pull it to inspect.

How old is the gas in the tank?

Additionally, these ECU systems are incredibly sensitive to vacuum leaks, have a look around the hoses to make sure everything looks good. Usually this will make it want to stall constantly but still something to check.

I guess you could check to make sure the VAF door isn't sticking either, that might cause the ECU to dump tons of fuel in.

Keep us updated!
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1.8L Turbo All Wheel Drive Capri... the "GTXR2"


LlamaLover

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    • 91 Capri XR2
Re: Rough idle + gas in tailpipe
« Reply #2 on: July 20, 2020, 10:11:47 PM »

Hey, thanks for the informative response! I'll do some of those checks tomorrow evening and see how it goes.

It did have about 3/16th a tank of several-year-old gas when I got it. I filled it the rest of the way and threw a cleaner in there. It was down to about 3/16th again when it started acting up, but I'd imagine most of the old gas would have found its way out by now.

I'll let you guys know how it goes, cheers!
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LlamaLover

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    • 91 Capri XR2
Re: Rough idle + gas in tailpipe
« Reply #3 on: July 22, 2020, 06:51:55 PM »

So, turns out I'm a dummy. I don't have a sense of smell, so I was going off what other people were saying. Smell of gas was definitely there the other day, but turns out that it is water and white smoke coming out of the tailpipe. Very small bit of white smoke also from under the engine somewhere.

Not really any smoke while idling, even if I rev in neutral. Just water in tailpipe, smoke comes once I go into gear and start moving.

Injectors sounded fine, no engine codes, and car is idling as normal. It did take a smidge of gas to start up one time today, but I don't think that's a big deal.

Gotta do some more reading tonight and see what I can check next time.
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Rocketman

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Re: Rough idle + gas in tailpipe
« Reply #4 on: July 23, 2020, 02:47:22 PM »

White smoke is usually coolant, blue smoke is usually oil.

Coolant could be an intake manifold or throttle body gasket leak. Could also be the head gasket.

Oil could be the turbo. Check the intake piping for excessive amounts of oil, some oil residue is normal. You can check the compressor on the turbo for shaft play by removing the inlet j pipe. Some side to side play is normal, should be no in/out play. If the turbo is showing wear get it rebuilt before it gets beyond rebuilding.

Regarding engine smoke: Check all the tiny coolant lines on the engine, and check to make sure the oil drain from the turbo isn't cracked and leaking onto the downpipe.
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1.8L Turbo All Wheel Drive Capri... the "GTXR2"


LlamaLover

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    • 91 Capri XR2
Re: Rough idle + gas in tailpipe
« Reply #5 on: July 23, 2020, 05:19:40 PM »

Oh, the turbo is definitely losing oil somewhere. That's been on my list. I thought it might be the return line, but could be anywhere really. I'll have to dig into it this weekend and check on the other things, too.

Thanks again for the help, I'll let you know what I find.
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LlamaLover

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    • 91 Capri XR2
Re: Rough idle + gas in tailpipe
« Reply #6 on: July 30, 2020, 06:18:21 PM »

So, coming back to update after finally cruising the Capri all day yesterday. I used the can and put a couple more gallons in it (was down to about 1/8th). It had puffed out a little smoke for about half a mile but started/idled fine. Filled up the tank at the station and there hasn't been any smoke since... Everything is running correctly and no real issues, so I'll call it a lucky win. For now. Definitely replacing a couple lines from the turbo that seem to be a little leaky, though.

Next step is cleaning out the headlight motors and replacing the old sealed beams with something that actually works!
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