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Discussion Starter · #1 ·
So it's never really gone away. I can clear the CEL, but it will crop up again as soon as I drive the car for more than a few minutes.

The dealer has replaced both the upstream and downstream O2 sensors. They also tell me that the plugs are properly gapped and undamaged (they're new with less than 2000 km on them). I can't speculate on the coil condition, but I did get a CEL (once) during winter startups telling me that I had a P0304 and P0300.... but those went away on their own and have never come back. So I'm going to ignore those for the time being. I used to habitually overfill the fuel tank, but stopped doing that last spring after I was told I was buggering up a fuel vent canister/filter. I have not paid to have it removed and/or replaced, and will keep that expense to the very tail end after all other avenues have been exhausted.

Back to the P0172... in communication with Toby at EC, he said he would be looking for an exhaust leak somewhere upstream of the primary 02 sensor (or close to the 02 sensor). Once gain displaying my ignorance of engine mechanical components, just what exactly should I be checking? I know where the primary O2 sensor is, but what exhaust connections should I be checking that are upstream of it? If anyone has the patience to deal with my stupidity, and you mark up a topside view of the engine and circle or point to what I should be looking at?

I'm a year late in doing this as well, but I need to do some pulls in 3rd to get some logged APR info for Toby to look at as well. At least that's something I know how to do and plan to tackle once the June monsoons are over with here in Calgary.

As always, I appreciate any feedback offered, and until I resolve this I'll continue to wear my tall conical hat and sit in the corner as punishment.
 

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I'm guessing cat connection to crosspipe or crosspipe to midpipe
 

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Discussion Starter · #3 ·
I'm guessing cat connection to crosspipe or crosspipe to midpipe
Appreciated.

So to confirm, upstream of the primary O2 is actually all the piping heading down out from the engine exhaust manifold on it's way to the cat? If so, I've got my head on completely bass ackwards. I was thinking the only stuff upstream would be the actual exhaust manifold. But, as I noted earlier, my mechanical aptitude is dismal at best.

Well, off to the dealership I shall go and have them check it out. If I can't get at things to inspect the connections from the top, it's better for them to go digging in the belly of the beast on my behalf. They have hoists.... I don't want to do this on my back using jack stands.
 

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Firstly, are you on the stock injectors?

P0172 is your ECU telling you the mixture coming straight out of the exhaust manifold but before the cat, is too rich. It could be an exhaust leak in the manifold, turbo flange or entry to cat. Leaking or otherwise faulty injector, or an issue with the engine harness.

Your misfire codes are not worth ignoring, and could be indicative of the source of your problem.

Check your fuel trims and AFR at idle and see how they behave. Note if this is happening on a warm or cold engine. Check your vacuum levels at idle as well.
 
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Discussion Starter · #5 ·
Firstly, are you on the stock injectors?
P0172 is your ECU telling you the mixture coming straight out of the exhaust manifold but before the cat, is too rich. It could be an exhaust leak in the manifold, turbo flange or entry to cat. Leaking or otherwise faulty injector, or an issue with the engine harness.
Your misfire codes are not worth ignoring, and could be indicative of the source of your problem.
Check your fuel trims and AFR at idle and see how they behave. Note if this is happening on a warm or cold engine. Check your vacuum levels at idle as well.
Thank you for the guidance. I'll add this to my documentation of what to look at.
In answer to your first question, yes, I'm using the OEM original stock injectors. The only things I replaced were the plugs and coils. Injectors are something I haven't replaced. As to when it occurs, it typically shows up after I've been driving for a while, then briefly stop and shut off the engine and then after a few minutes perform a restart. It then hesitates to start up and then runs rough for a few minutes, and then seems to smooth out. The misfire codes, including the one specific to cylinder 4 both triggered at the same time... and only once. They've never re-appeared. So far....
 

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Install stock tune, see if it goes away.
 
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Try the stock tune, but I’m honestly leaning towards an injector issue at this point. It could be dumping way too much fuel into cylinder 4 causing all that unburnt fuel to trigger your fuel trims and system rich code.

Injector issues are not uncommon, my cylinder 4 injector was faulty on a 3k engine.
 
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Discussion Starter · #8 ·
Install stock tune, see if it goes away.
I did. It didn't. Hence the journey down the rabbit hole again. For the relative minor cost involved, I think I'm going to start with replacing the #4 cylinder injector and see what shakes out of the tree after that.
 

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Discussion Starter · #9 ·
Try the stock tune, but I’m honestly leaning towards an injector issue at this point. It could be dumping way too much fuel into cylinder 4 causing all that unburnt fuel to trigger your fuel trims and system rich code.
Injector issues are not uncommon, my cylinder 4 injector was faulty on a 3k engine.
Thank you for that... I think I'll try a new injector as my first step. Not huge money and quick and easy to do. Fingers crossed.
 

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Discussion Starter · #12 ·
A list of possible causes straight out of the workshop manual.
Yup.... matches what was in the MOPAR Service Manual I have as well. I have one of the USB versions they used to sell. Off topic, but the USB version I have is locked down by whoever designed it for them so it will only run with Internet Explorer... and now that IE's been given the kiss of death by Microsoft, I've been trying to get it to run in Edge using the IE compatibility mode. No joy in Mudville on that front (yet), but that's the least of my worries. I can always keep an old laptop kicking around with a copy of IE on it to use when I need to.

So, off to the dealer tomorrow to order an injector and get an installation scheduled. I am praying that this is the solution to the problem, as that would be such an easy fix (all things being relative).
 

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Abarth 124 Spider Turismo, 02/2017
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Looks like either not enough fuel is being burned up when ignition occurs or your Injectors are not closing properly, which can lead to injection-leakage at all times.

A recommendation:

-There are Injector-testers and some good equipped dealers. Let them check for leakage or bad spray-pattern.
-Check the Spark-plugs and coils if they produce enough of an arc to ignite all the mixture.
-(AT YOUR OWN RISK) If they cant test it, plug off all Coils, take out the Injectors and use large towels or smth. absorbant, non-flammable and then, with the help of a second person, try to crank. Normally the ECU should actuate all 4 injectors and from the patterns they leave on your towels/whatever you can see bad injectors at the beginning. Once its soaked replace it a second time and try it again. If the patterns are all the same you should be good on them.
- For the Spark-plugs take out the gaspump-fuse, take out the coils and plugs, reconnect them together and hold it to mass with the front-side. Normally you should have equal sparks on all 4. if 1 of them looks weird, too dim or doesnt ignite in the same rhythm than the others its defect and you should replace it.
-But proceed with changing that injector out, as suggested by the others.

Otherwise, same problems can arise from:

-Rodent-damage
-Valves are not properly shut, can happen through burned up residues or damage to the valve-seats, you would have to use grinding-paste to fix that or bring it to a dealer.
-And be sure that your tunes are properly tuned up.

Whatever, lets see what your dealer says.
 

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2018 White Lusso Plus Auto , Tan Leather
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As a totally old school thought, i had a 90s car that would start and run ok but if i stopped and then restarted the car used to run lumpy as hell. Turned out the engine temp sensor thought the engine was cold and effectively ran with choke full on. A very rich mix. The car didnt have diagnostic codes so took a while to find.
Good Luck
 
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