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Hi guys,
I switch my car on in the morning. Very lumpy idle for around two mins. After it starts to warm up idle goes smooth. This problem seems to be around the same time that I noticed an exhaust ticking.
There are definitely no vacuum leaks as I’ve checked all the pipes and their correct routing.
I popped my head in the engine bay at initial start up from cold this morning and I got my hand around the exhaust manifold. I couldn’t feel it blowing on my hand but I definitely smelled exhaust gas with my nose above the manifold.
My theory is that I have a slight exhaust manifold leak and that leak is causing the O2 sensors some fuel ratio problems hence causing the lumpy idle. After a few minutes the heating up closes the leak and that’s why my idle returns to normal.
Would folk agree with this based on the evidence I’ve observed?
Thanks in advance
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[quote=”Webby the Bear” post=139381]Hi guys,
I switch my car on in the morning. Very lumpy idle for around two mins. After it starts to warm up idle goes smooth. This problem seems to be around the same time that I noticed an exhaust ticking.
There are definitely no vacuum leaks as I’ve checked all the pipes and their correct routing.
I popped my head in the engine bay at initial start up from cold this morning and I got my hand around the exhaust manifold. I couldn’t feel it blowing on my hand but I definitely smelled exhaust gas with my nose above the manifold.
My theory is that I have a slight exhaust manifold leak and that leak is causing the O2 sensors some fuel ratio problems hence causing the lumpy idle. After a few minutes the heating up closes the leak and that’s why my idle returns to normal.
Would folk agree with this based on the evidence I’ve observed?
Thanks in advance[/quote]
What is the year, make, model, mileage of the vehicle?
And you say the idle smooths out after coming up to operating temperature?
[quote=”Webby the Bear” post=139381]… and that leak is causing the O2 sensors some fuel ratio problems hence causing the lumpy idle. After a few minutes the heating up closes the leak and that’s why my idle returns to normal. [/quote]
The only problem is, the O2 sensor data is ignored by the computer until the engine is warm and goes into closed loop operation. Your issue occurs at cold start, so O2 sensor data wouldn’t factor in.
Fix the exhaust leak first. It’s a safety issue, but it won’t fix your problem.
Once that’s taken care of, you can begin troubleshooting your cold idle issue in earnest.
[quote=”cap269″ post=139396][quote=”Webby the Bear” post=139381]… and that leak is causing the O2 sensors some fuel ratio problems hence causing the lumpy idle. After a few minutes the heating up closes the leak and that’s why my idle returns to normal. [/quote]
The only problem is, the O2 sensor data is ignored by the computer until the engine is warm and goes into closed loop operation. Your issue occurs at cold start, so O2 sensor data wouldn’t factor in.[/quote]
That is an excellent point!!!
Thanks for that.
As I’ve got no vac leaks and I’ve cleaned my ICV I’m wondering where to go now :unsure:
…I believe this was sold in the states as a ”Catera” but don’t quote me on that lol
Just to recap…
Definitely got no air leaks as I’ve tested for them and nothing leaking.
ICV replaced (I had a spare so thought I’d put it on)I looked at the fuel trims yesterday… car goes in to closed loop as it gets up to temp (as expected) and o2 sensor switching nicely between 0.12v and 0.82v.
Check the EGR valve. The diaphragm may have ruptured. That could cause your exhaust smell up front also.
Thanks cap.
its not a vacuum operated one but it’s something to check. can I spray carb cleaner around it and the exh. manifold in search for the leak? like looking for a vac leak?
That could help determine if it is a gasket that is leaking, but to test the electric EGRs you have to remove them (for a visual inspection of the underside) and test resistances.
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