North American Turbocoupe Organization



Intermittent running rich issue..
Kuch Offline
Senior Member
#1
So driving home in my 88 the other day and I felt a slight stumble while just driving slow in 2nd gear through a village. Took note of it, but had to drive home from work, then a little further it stumbled more and more and the wideband was pegged down at 10 AFR. Typical rich exhaust and ran like crap, but it would run fine intermittently like something was switching on and off. Made it to the driveway and noticed the primary fan was running, even though my water temps were low to normal. I could hear the fan relay clicking on and off at random times and the engine would clear up and run fine, fans turn on engine runs rich, fans turn off goes back to normal. Which is why I posted a WTB for an IRCM, but now thinking it may be something else, possibly the ECT sensor going bad and tricking the engine into a cold run mode but still triggering the fan on? I haven't pulled codes yet, but not sure what I would see except running rich. Would a bad ECT sensor cause this issue? Could I unplug the sensor and run it with a jumper both installed and not installed to see if it clears it up? I know it's an electrical switch of some kind as it is intermittent and the fans kick on when it goes real rich and back to normal when they switch off. Thoughts? Thanks
1988 Turbo Coupe, Black/Black, 5 Speed, Moonroof,  T3/T4 50 trim, ported E6, 255LPH, Kirban, 3" DP dual 2.5" w Hooker Maxflows, MGW shifter, K&N, Gillis valve, RR cam, Koni's
1964 Ford Galaxie 500XL, 390 6V, Big Solid cam, Headers,3.89's, 4 Speed, Vast and fast
1960 Ford Starliner, 292 Y Block, 312 4bbl intake, headers, 3 Speed, slow and low
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Mikey97D Offline
Member
#2
Isn't there 2 coolant temperature sensors? One close to the intake manifold and the other towards the front passenger side of the motor?

Edit: does your idle change too for no reason?
1988 TC, 5 spd, Stinger 3" Exhaust, Schneider Roller Cam, -4° Cam Pulley, Cone Filter, Gilles Boost Control Valve set at 17 psi, [font=medium-content-sans-serif-font, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen, Ubuntu, Cantarell, "Open Sans", "Helvetica Neue", sans-serif]Walbro 255 lph, [/font]CHE Rear Lower and Upper Control Arms, Braided Brake Lines, Hawk HPS 5.0 Front and HPS (F) Rear, CRES Inserts in front calipers, and '93 Cobra Wheels with General 235/50R17 Tires.   
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spittinfire Offline
Junior Member
#3
It honestly sounds like an electrical connection or a grounding issue on the sensor for the ECM. It may not be the sensor itself but it sounds like that circuit would be a good place to start looking. A sensor is cheap so you could try changing it and while you're there check the plug for burnt terminals and loose wires, it's not uncommon to have to install a new plug. I had to put a new plug on the sensor wire for my gauge not long ago, now my gauge works.
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Kuch Offline
Senior Member
#4
yeah, I agree with an electrical connection or a bad sensor, just really hate chasing electrical problems. I cleaned, sanded, and re-attached my underhood grounds in the spring as well as adding an extra ground from the intake to the fenderwell, so those should be good to go. While it was running like crap, I did the usual test of wiggling different sections of harness to see if it changed anything, but nothing, even at the ECU in the pass kick panel, so I don't think it's a broken wire somewhere.
1988 Turbo Coupe, Black/Black, 5 Speed, Moonroof,  T3/T4 50 trim, ported E6, 255LPH, Kirban, 3" DP dual 2.5" w Hooker Maxflows, MGW shifter, K&N, Gillis valve, RR cam, Koni's
1964 Ford Galaxie 500XL, 390 6V, Big Solid cam, Headers,3.89's, 4 Speed, Vast and fast
1960 Ford Starliner, 292 Y Block, 312 4bbl intake, headers, 3 Speed, slow and low
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vegas_ss Offline
Senior Member
#5
Check for any stored codes which may point to the area to investigate the wiring. I had issues with the wiring harness connection by the upper/lower intake although I was getting a check engine light for that. Perhaps an intermittent injector problem? Test the fuel pressure and see if it holds after the key is turned off which may point to an open or stuck injector. You could take a look at the plugs and see if any show a rich condition more than the others.
1987 TC, 5sp, Boport Stage 3 Head/2.1 Cam
1996 Impala SS
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Kuch Offline
Senior Member
#6
I pulled all the plugs and everyone was black and sooty, so each one is running rich. fuel pressure gauge mounted on the fuel rail showed 39psi running and held pressure, but not sure how long it should hold pressure for, 1 hour, 2, overnight? Still haven't pulled codes though, another car project has me distracted, Ford Expedition service advancetrac light came on the dash, when it rains it pours.
1988 Turbo Coupe, Black/Black, 5 Speed, Moonroof,  T3/T4 50 trim, ported E6, 255LPH, Kirban, 3" DP dual 2.5" w Hooker Maxflows, MGW shifter, K&N, Gillis valve, RR cam, Koni's
1964 Ford Galaxie 500XL, 390 6V, Big Solid cam, Headers,3.89's, 4 Speed, Vast and fast
1960 Ford Starliner, 292 Y Block, 312 4bbl intake, headers, 3 Speed, slow and low
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vegas_ss Offline
Senior Member
#7
As long as the pressure holds for a few minutes and you don't see a steady drop that would be fine. Would seem that something is requesting more fuel than needed which would be either the intake air flow is being over reported or O2 sensor is reading lean. Sorry can't offer up anything more at the moment.
1987 TC, 5sp, Boport Stage 3 Head/2.1 Cam
1996 Impala SS
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Kuch Offline
Senior Member
#8
going to check my VAM for smooth movement as well as the voltages too. O2 sensor was a new Bosch installed 2 years ago, hope that is not bad already. I keep thinking the ECT because of the fans turning on when it is running real rich, and they go off and it runs great again.
1988 Turbo Coupe, Black/Black, 5 Speed, Moonroof,  T3/T4 50 trim, ported E6, 255LPH, Kirban, 3" DP dual 2.5" w Hooker Maxflows, MGW shifter, K&N, Gillis valve, RR cam, Koni's
1964 Ford Galaxie 500XL, 390 6V, Big Solid cam, Headers,3.89's, 4 Speed, Vast and fast
1960 Ford Starliner, 292 Y Block, 312 4bbl intake, headers, 3 Speed, slow and low
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Jeff K Offline
Administrator
#9
You may be on to something with the ECT. ECT is just a thermistor. Resistance drops exponentially as temp increases. You can remove it and measure its resistance. Measuring resistance with ECT in the intake manifold is a PITA, IMO. Room temp should be several thousand ohms (like 10K+ ohms) and if you put it in hot / boiling water should be a few hundred ohms.

Break in the ECT harness or poor ECT connector connection at ECT will also lead to high ohms and the PCM will think engine is cold.

May also want to check the coolant bung sticking out of the intake right under the ECT to be sure it isnt plugged with goo. ECT depends on coolant flow thru that bung to get a correct temp reading. When I got my TC 21 years ago, that bung was 90% plugged with crap and the hose to the bung was 50% plugged with crap.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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Kuch Offline
Senior Member
#10
Jeff,
You make a great point on the coolant passage in the intake, I actually just posted this earlier today about what I found. https://turbotbird.com/thread-intake-coo...#pid258992
1988 Turbo Coupe, Black/Black, 5 Speed, Moonroof,  T3/T4 50 trim, ported E6, 255LPH, Kirban, 3" DP dual 2.5" w Hooker Maxflows, MGW shifter, K&N, Gillis valve, RR cam, Koni's
1964 Ford Galaxie 500XL, 390 6V, Big Solid cam, Headers,3.89's, 4 Speed, Vast and fast
1960 Ford Starliner, 292 Y Block, 312 4bbl intake, headers, 3 Speed, slow and low
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