75ohm

Touched base with Pete last night, he's been tied up -- his car is still at the shop...

PeteL

"Pete, systematic diagnosis. You said it runs fine when cold. So that would mean that whateve the problem is has to with something that does not come into play until the car is at operating temp. The TPS does not change function based on coolant temp. When the coolant is below 90 degrees, it is in "open loop" meaning it goes on a preset fuel/ignition timing map. Once the engine is in "closed loop" it starts to look at air volume (air flow meter and thermometer that is in it) The DME derives air flow mass from a volume@temp reading. Then looks at the exhaust gas content to determine if the mixture is stoechemtric 14:1. If it is rich, it will close the fuel injectors early, lean it will keep them open. Ours fire injectors 1&3 together and 2&4 together. BTW did you ever change the DME coolant temp sender? Also of value is testing the injector pulses, you can check this with a NOID light. Or when the vehicle is at operating temp, start by disconnecting one injector at a time and see if the problem changes. That test could fail, if an injector is stuck open it will not show a change when unplugged."

-- Yes it has always run better when cold. When it is cold outside the car rocks!! When it gets hot (as it sometimes does in FL), performance really falls off. During the summer, in the morning, fresh out the garage, the car is great. On the way home, after sitting in the parking lot, not so great.
Thanks for the suggestions. We have looked at injector pulse, which was fine, also fuel pressure which was also great.
We have established that it appears the car is running on the lean side.


"I'm gonna throw out Fuel Pressure Regulator. $60 @ any autozone" -- what is your thinking behind this? I have been through a few FPRs over the years, and the symptom has always been running like on 3 cylinders when cold. The car is starting and idling fine on cold startup.


"I'm not wasting any more of my time. OP hasn't bothered to post back in 2x weeks or answer questions or even offer any thanks !.
guess his car is running ok now huh?! " Thanks for your interest in this. I do appreciate and read all of the input. I have been unusually busy - had a step-daughter graduate HS, dance recitals, life stuff. With the car at the shop, where they check things on a part-time basis (Not the focus of their efforts as it is not a daily driver) we are not making steady progress. Next up for checks are grounds and temp sensor.
I drove the car around mid-day Saturday to see where we are. It was hot outside, and the car just will not accelerate, unless you rev to 4K and go. Otherwise it can't get out of it's own way.

peanut

dayum ..guess that means I gotta apologise to pete huh!?

soooorrrrrrrrrrrreeeeeee

If the engine is still running lean it has to be something to do with the fuel delivery which is metered by the ECU . The ECU increases and decreases injector pulses in direct relationship with the electrical imputs from all its sensors.

Have you checked that there are no missing heat shields to the fuel delivery pipes and rail ? Just looking outside the box for a mo. Have you checked that the fuel tank breather isn't partially blocked ? a vacumn can build up pretty quickly.

I will check the Bosch 'book of magic' later but I am still inclined to think that one of the sensors is giving false info to the ECU when the engine temperature rises. Have you tried repacing the o2 sensor ?

PeteL

I think it is a sensor too. The O2 sensor is about a year old.
My leading contender is the temp sensor. Stay tuned.

peanut

well i've re-read the book of words of bish bosh and from the symptoms you describe it is likely to be one or all of the following.

1.) Air leak in the vacumn system or inlet manifold. Suggest you do a thorough check of all the pipes and connectors maybe attach a vacumn guage and check .
2.) Faulty AFM or AFM setting . Suggest you remove the AFM and check the reading throughout the wiper range and check the correct setting as per the guide on Clarkes garage.
3.)check the flow and spray pattern of the injectors to make sure you are getting a even distribution and sufficient flow.
Remove each injector connector in turn whilst engine running see if there is any variation in rev drop.
Check the plugs for lean mixture particularly in one bore which could indicate a partially blocked injector.

PeteL

OK...thanks. We have ruled out the vac leak.
The AFM is a potential problem. We swapped with another AFM...and the car ran worse, but not sure of the history of that one. I did in the past check the installed AFM per Clarks' garage and it checked OK.
Plugs removed and changed. Old ones passed muster.

We can revisit the injectors. But not seeing anything that raises concern with them.

I would like to swap in a known good AFM. But don't have access to one.

peanut

how did you rule out the vacumn system ?did you use a vacumn guage ? how about the injectors . Did you do a fuel pressure leak down test ? Don't assume your AFM is still ok because you tested it before, its the hot favourite to be the problem

PeteL

vacuum verified by gauges, did a fuel pressure leak down.
Checked injector pulse.

I can see the AFM being bad. One of the few items in the FI chain that hasn't been changed in the 12 years I have had the car.

I will check it again. Definitely makes sense, as it seems the computer info is not matching reality. Ie seeing more or less air than is really being introduced.

KuHL 951

I had a bad AFM door on my black 951. It would not close all the way due to a weak spring making it run rich at idle; under full throttle it would swing much too easily causing a false signal sent to the DME where it just kept dumping fuel to keep up with the false air signal. It's worth a shot to check that door...it should slam closed and seat with a very positive sound against the stop. A spare AFM cured everything for me and it passed smog easily for the first time in years.

harrisonrick

While you`re in there, do that sweeper arm clean-up service...that arm may have grooved out the plate, and it won`t be getting a good reading.

PeteL

There was a significant difference between the door motion on the 2 AFMs. The one in my car had more resistance (harder to move), while the one that we put in, and made the car run worse, had a more free moving door.

75ohm

Pull the spare apart and check its functions...

PeteL

Going to check that AFM tonight.

75ohm

I'm off all next week... want to check the DME/wiring?

PeteL

Yes!!