2.7i swap drivability issues

[Swanny]

A few months ago I completed the swap over a weekend for my brother. His 86eta was acting like crap and I had the parts to convert to a 2.7i using an 87i harness, ecu from the 87i (173), and an 89 885 head. Swap went well but of course his tach has never worked as the car has a million electrical gremlins that I'm slowly working out for him (he lives in Nashville and I'm in upstate NY).

Issues I'm a bit stumped with are these. Under decent acceleration the car decides to cutout/misfire/buck like slammin' when he's visiting blunt. Hooked up a fuel pressure gauge as I imagined a starvation problem but it stays rather consistent as seen in the video. Like mentioned earlier his tach never worked and I'm also on the hunt for that so see exactly when this thing drops out.

The other thing I've noticed is his oil pressure light will tweak out while this is occurring, similar to when the car stalls.

Built a smoke tester and it seems that all vacuum leaks were cleared up last time I was visiting.





Suggestions of other places to start are greatly appreciated! I have to head back to NY tomorrow and would at least like to get dome of this cleared up before I head out.

[Gary Horneck]

Sounds like a AFM problem. Which AFM did you use on the swap?

[Swanny]

Sounds like a AFM problem. Which AFM did you use on the swap?

Afm from an 89i. Resistance seems ok on the potentiometer at ~2k-3kohms when moving from open to close. The temp sensor though is only giving about 500ohms and its about 70 here now.

[Gary Horneck]

That's low by 2000 ohms I think. ECU thinks the incoming air is very hot?

[nando]

resistance decreases with temp, it doesn't increase.

[Swanny]

So I managed to stall this thing while out test driving it and now it cranks and sputters but won't stay running....checked connectors and saw nothing loose. Fuel pressure gauge is still in the proper range. Will try the CPS when/if I get back to his place.

[Swanny]

Ok cranked on it for about 1minute and it kicked back to life...sooo alright! Will see if it's a warm start issue in a minute.

[Gary Horneck]

resistance decreases with temp, it doesn't increase.

I meant... if room temp ohms should be in the 2200-2700 ohm range, and he is reading 500 ohm at room temp, the ecu is thinking the intake air is very hot.

[nando]

ah, I get you. I believe the Bentley has the resistance it should measure at room temp.

[Swanny]

Doesn't want to start as soon as I parked it in the drive way. After another long hard crank it eventually decides to.

[nando]

I'm not sure that IAT affects starting - usually coolant is the only factor since airflow during cranking is minimal.

so, the question is - are you getting fuel pressure during cranking? is the CLT sensor working?

[Swanny]

I meant... if room temp ohms should be in the 2200-2700 ohm range, and he is reading 500 ohm at room temp, the ecu is thinking the intake air is very hot.

Gary is correct with that number, unfortunately I don't have a scale of what resistance matches perceived temperature by the sensor.

[Gary Horneck]

Here's the table I have -
Temperature Minimum Resistance Maximum Resistance Tolerance
0°C 32°F 5.0k 6.2k 10%
20°C 68°F 2.2k 2.8k 10%
30°C 86°F 1.5k 1.9k 10%

The IAT does affect timing, so...

[Swanny]

I'm not sure that IAT affects starting - usually coolant is the only factor since airflow during cranking is minimal.

so, the question is - are you getting fuel pressure during cranking? is the CLT sensor working?

Yes, pressure is constant the entire time. But now of course the pressure tester decides to act like a damn fool after I took it off and reattached it.

[Swanny]

Here's the table I have -
TemperatureMinimum ResistanceMaximum ResistanceTolerance
0°C32°F5.0k6.2k10%
20°C68°F2.2k2.8k10%
30°C86°F1.5k1.9k10%

The IAT does affect timing, so...

Thats a great place to start! Now to find an afm in nashville try out.

Paging agent, slideways and all you other guys!