I have a 98 Grand Cheerokee (V-8) with 127K on it, that sometimes during cold starts acts like an old carburetor system with the choke sticking. It floods, chokes, it sputters, and you have to maintain an RPM of about 2000 to keep it running and get it to snap out of it. A local shop did a tune up on it before this problem started to happen intermitently, aside from this it seems to run well. I took it back to the shop and they did several diagnostic test and even got it to do it for them while they had it. I told them that it seemed like if we released the key from the start position as soon as it began to fire, the problem would happen,if we held it in start for a bit longer we could usually avoid it. They returned it to me saying that “Yup, if you hold the start position longer it won’t happen, and by the way here is a bill for $103.” With the recent below zero temps its getting worse, almost unavoidable. My wife says it uses a lot of fuel when this is happening but we have not actually tracked the mileage. Other than this its a great car but I’m ready to drive it off a high mountain cliff. HELP!
If your wife says it uses a lot of fuel, that’s an indication that the engine is running abnormally rich. That can be caused by a bad coolant temp sensor, or a “lazy” oxygen sensor which is under-peforming, but is not bad enough to set the “check engine” light. A lazy oxygen sensor will cause the computer to default to running the engine in a fuel-rich condition, which results in poor gas mileage. Find a shop with a scope that can test your oxygen sensors thoroughly.
Others can correct me, but I think I learned on this forum that if you hold the pedal to the floor while cranking the engine, that sends a signal to the computer to act as if the engine is flooded. Doing so may help you get it started more easily/reliably until the root cause is found.
I’m not convinced it’s running rich.
When it acts up is there gray or black smoke? Does the exhaust smell like raw gas?
Most computer controlled engines run richer when keyed in the start position.
It could be it’s going lean when the key is released from ‘start’.
We dont really see any smoke but it does smell of gas. I do believe that it is running rich and think the O2 sensor idea may be going in the right direction. NAPA tells me there are two O2 sensors, one located before the cat converter, the other after it. I can replace both for about the price of another “diagnostic fee” at the repair shop. I will go down next week and ask the owner of the shop if they will check it out again without charging me more for anything other than the actual repair. Thanks for the help.
If you smell gas the fuel mixture is way too rich. And the problem isn’t with the O2 sensors. The O2 sensors don’t come into play until the engine is up to operating temperature. So if this occurs during a cold start, it’s not the O2 sensors.
You might have the fuel pressure regulator checked to see if it’s diaphram is leaking. If it is, this can force gas into the engine while it sits. And then when trying to start the cold engine, not only is there fuel already sitting in the engine, but more fuel is being added when trying to start the engine. This then causes the engine to be hard to start, there’s the smell of gas, and it runs rough once it starts.