Readings seem fine - why so rich? (Page 1/4)
tnkgnr MAR 20, 08:50 PM
Hi all,

I'm trying to diagnose why my car is running so rich - it's kicking out black smoke...and I'm pretty much out of ideas. I have a 3.4l pr that has sprint headers. I've ported out the intake manifold a little bit to match the gasket lines. There are roller tip rockers and PO said there's a crane cam in there, but I don't know the exact one.

My running rich problem came after I put in new injectors (they're the 17lb BMW ones). Previously I was getting detonation with even moderate amounts of load. The new injectors solved that and I had gobs more power for a couple days. Then I went out and all of a sudden the car was bogging down and bucking, and barely keeping an idle.

I've tried electrically disconnecting the MAP sensor and when I do, the car seems to run just fine - no smoke. I've also checked that vacuum line and it sticks to my finger. In the readings below, it seems like it's functioning normal right? (4.75v at engine off, 1.88v at engine idle)
Other sensors seem to be fine too (coolant, TPS goes through the whole range smoothly with throttle input). O-2 sensor I installed today. Note the MAP errors were from me disconnecting it.

Any ideas?

Engine off


Engine idle
Patrick MAR 20, 09:13 PM

Are those coolant temperatures Celsius or Fahrenheit ?
tnkgnr MAR 20, 09:15 PM
Both - top one is Celsius, bottom is same value in F.
Patrick MAR 20, 10:32 PM

So the coolant temperature is being reported as less than 114°F? Is this supposed to be a warmed up engine?
tnkgnr MAR 21, 08:19 AM

quote
Originally posted by Patrick:


So the coolant temperature is being reported as less than 114°F? Is this supposed to be a warmed up engine?



The engine is not fully warmed up in those pics. I had run it earlier to full temp (and got the code 45 - rich). Just didn't want to cloud up the garage again, but I can if it's helpful.

Patrick MAR 21, 02:54 PM

The A/F mixture will be influenced by both the MAT and coolant temperatures (a colder engine requires a richer mixture), so it's important to know what readings are being sent to the ECU when the engine is fully warmed up.

I also like to occasionally check the MAT and coolant temperatures first thing in the morning after the engine has sat all night, to make sure these two readings are very similar. The engine isn't running for this test. If the readings of the cold engine aren't close, at least one of the temperature sensors is probably faulty.
tnkgnr MAR 21, 07:57 PM

quote
Originally posted by Patrick:


The A/F mixture will be influenced by both the MAT and coolant temperatures (a colder engine requires a richer mixture), so it's important to know what readings are being sent to the ECU when the engine is fully warmed up.

I also like to occasionally check the MAT and coolant temperatures first thing in the morning after the engine has sat all night, to make sure these two readings are very similar. The engine isn't running for this test. If the readings of the cold engine aren't close, at least one of the temperature sensors is probably faulty.



183 on the coolant, 77 on the MAT. Might not have fully warmed up, but this was after a few minutes. I think the temp sensors are doing okay. As it has sat in the sun, the MAT is now up to 90 and the coolant down to 110.
tnkgnr MAR 21, 08:01 PM
BTW - I sat on that above post for several hours - not 90 degrees at 8PM!

For what it's worth, I pulled vacuum manually on the MAP sensor just to be sure. Pulled smoothly down to 1v with 25mm Hg.
tnkgnr MAR 23, 07:20 PM
Cold start injector is removed. Distributor, coil, wires, plugs all new and gapped to .045.
Dennis LaGrua MAR 23, 08:07 PM
Are those BMW injectors high impedance? They must be high impedance for the engine to fuel properly. Are they new or used? There are three types of fuel injectors, Pintle, Ball and Seat and Disc. The OEM Fiero ECM is set up to control the Bosch Pintle style. If you are running the correct injectors then test for leakage and check out the sensors as suggested in this post.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "