Hello. Zoot has been part of the family for about 3 weeks now. I knew he was going to be a project but now I just want to get him Daily Driving.

Here's whats been done so far:

Plugs
Cap
Rotor
Wires
Belts
Air Filter
Fuel Press Regulator
Fuel Filter
Main Fuel Pump Replace
In Tank Pre Pump Replace (New Screen)
In Tank Sending Unit Replace
Tank Lowered,Drained Cleaned
Ran Snake Oil Fuel Cleaner through 1 tank of fuel.

So here's what's going on. He starts out and digs running on the highway for 10 miles or more. 60-80MPH...He has gone 100 ;-) When I come to a slow down or back to surface streets and hot a light, the skinning pedal causes it to stumble and seems like fuel delivery trouble. I pull over, kill the engine, wait a second and fire back up and he run perfectly for another 30 mis, 2 hours...a few lights....and then the acceleration stumble returns. I'm thinking a faulty TPS. What would you guys recommend? I'll admit, I haven't done a complete diagnostic with the little test box under the hood.

Any and all recommendations appreciated. Gotta make Zoot happy.

 

Forgot to mention that Zoot is a 91 240. I also installed a new alternator that is for sure working.

 

"the skinning pedal" ??

 

the TPS is purely an on/off switch that detects if the throttle is at idle or not. easily tested with an ohm meter, it should click 'open' nearly the instant the throttle comes off idle.

I'd be more inclined to suspect the IAC (Idle Air Controller), this is a solenoid actuated air valve that bypasses the throttle. its under the intake manifold. it tends to get gummed up, and cleaning it out with some throttle/carb cleaner spray can do wonders. make sure both short rubber hoses are intact and not cracking.

 

Thanks Pierce I'll look into it. Skinny pedal...I don't know why I typed Skinning.

 

I do believe I'd check the OBD reader under the hood and verify there are no codes on either the EFI (pin 2) or ICU (pin 6) side. takes about 2 minutes and requires no tools.

Engine and OBD Diagnostic Codes and OBD Diagnostic Codes

(most all 1989+ 240's are LH2.4, which is the same as 1989+ 740/940's...)


another candidate for your stumble-off-idle is intake air leaks, like vacuum hoses, crack on the main air plumbing between the MAF and the throttle body, etc.

 

Ok I get a 3-1-1 on test function 1

Vehicle Speed Signal Missing------what next?

Piece, I can hear the injectors and the IAC cycle during OBD testing....should I still pull that and clean it? I don't want to clean the MAF right now for fear of making stuff worse.

Also since I replaced the bulbs in the cluster...the brake failure light is on. I know it needs new pads which I am getting to soon.(Parts on hand).
Is this Vehicle Speed Sensor tied to the brake circuit some how?

Speedometer has always been working on this car, I replaced the Odometer gear and then I lost my temperature gauge, I had to use part of another cluster to get things working....when it went back in, the temp gauge is a bit intermittent and the ODO stopped working after I got it going again. Still have Speedometer

 

Ok found bad wiring at the VSS....cleaned up and heat shrinked...OBD code for VSS gone but car is still funky.

Running great at all different speeds for 10-15 minutes. Out of nowhere comes a stumble and when I give it gas it bogs....if I back off just a bit before idle...I can get it down the road another few miles. I pull over, cycle the ignition key, and he fires right up running great at all speeds for another 10-15 maybe even an hour or only 5 minutes and it starts sputtering. Fuel tank at full level.

 

that sounds VERY much like clogged fuel system. I'd be checking fuel pressure and fuel flow. yes, I know you replaced all that stuff, but new parts aren't always good parts.

 

Pierce, it's almost as if I can predict when it's going to start weirding out. It's about the same Time elapsed when it does its thing. Ok, I took off and cleaned the TB, The IAC, Flame trap. Didn't squirt the MAF since it looked very clean. I replaced the accordion hose to the TB, the TStat in the air box. Cleared codes and ECU (Batt off while I was cleaning and replacing) Seemed to run pretty well for 10 miles, then the familiar stumble and doo doo performance. Pull over cycle ignition, up and running again. IDLE was high after 10 minute ride, I pulled the plug on the MAF and the idle lowered but seemed to miss a little bit.-Obviously the CEL came on, replugged MAF and cleared CEL.....runs good, does the 10-15 hiccup routine.

I am now thinking I need to go back into the tank and replace the darn coupling hose to the prepump and sender, that or I need to replace injectors?

 

Oh, the Vehicle Speed Signal code popped back up on OBD

 

Went for a ride today. Car ran good through all speed ranges for 15 mins. Coming home at an extended light, the idle stumbled and lost continual rpm until it staled out. A quick on off cycle of the ignition and he runs great the rest of the way home. In driveway-Idle fast.

Not sure what to do next.
Pierce, fuel pressure testing is a must? Best method? This is my first Volvo experience..never had so much initial trouble from my older 4runners. I absolutely love this car and I have been a truck guy for 25 years. I am a recreational mechanic just because I am a cheap bastard and wont pay a shop to replace parts. Should I replace all the vacuum hoses? Will the intank fuel pump cause this at any fuel level?

 

well, a fuel pressure test would either show a definite problem that could be tracked down and fixed, or it would suggest the problem is somewhere else and not fuel deliver related.

you need a fuel pressure test gauge, with T adapters suitable for volvo fuel fittings. you disconnect the main fuel line where it goes onto the fuel rail, and connect the T fitting. a good FP gauge also has a vacuum line you'd connect via a t-fitting to the vacuum line that connects to the fuel pressure regulator. then you'd start the car and monitor the pressure. optimal is 42-46 PSI relative to manifold vacuum (hence the vacuum fitting).

I generally bring the car to a mechanic for this sort of diagnostic, as he has these sorts of speciality tools. They aren't cheap and I've not been able to justify buying them myself for the couple cars I maintain.

 

Haven't found the Fuel Pressure Testing Mechanic yet. I've been fiddling with the Instrument guage...not sure why but now I get a CEL for about 2 minutes then it goes out. The CEL bulb has always been functional and would light up on Key II but never came on when the engine was running.

 

have you checked the OBD code reader to see if there are any engine codes on pins 2 or 6 ? no tools or equipment required. see Engine and OBD Diagnostic Codes for the procedures and codes.

 

Ok Pierce I checked it out again. The only code that comes up on pin 2 with 1- one second push is a 3-1-1. All other tests check out or sound out. The only other observation I made was when the 6 pin is testing out puts to injectors and IAC...the IAC seems like the first 2 times it cycles, is not as strong as the last 2 times it cycles. I have taken this off and cleaned it well. So the 3-1-1 code on your instructions says:
3-1-1
Signal missing from speedometer Speedo wiring or instrument cluster wiring faulty Idling problems.

In the Bentley's it says Vehicle speed signal missing. Now I did find bad wires back at the differential where the speed sensor is located, but the code came back up on OBD after repair and clearing. DO I need a new speed sensor in the differential? The Speedometer is functional in the car. Would this sensor cause my woes? Should I replace the IAC? I've cleaned up Flame Trap, will the Oil Sep Box cause any issues like this other than PCV blockage and oil leaks???

 

looking up the greenbook wiring diagrams of a 1991 240 (I have these on DVD)....

ok, if the speedo is working, the sensor is good, the speed sensor signal goes from the pickup on the differential to the speed sensor, then from the back of the instrument panel, connector '31' pin 6 goes to ECU pin 34 via a blue+black wire. connector '31' is the circular connector on the back of the instrument panel. this same signal also goes to the cruise control, if you have one.

the ECU is up against the right side of the passenger footwell, behind the plastic side panel (remove the felt footwell liner under the dash, remove the plastic door sill, and lift up the black rubber gasket along the front edge of the door frame til this panel comes free, and its right there). according to my reference, 3-1-1 can cause flakey idle.

if the oil seperator box isn't cracked, and you cleaned it out, and your flame trap is unplugged, then you shouldn't blow the oil seals. this is the crankcase ventilation on these cars, and if its blocked, the pressure has to go /somewhere/ so it has a tendancy to pop out whatever seal it can.

genreally cleaning the IAC and verifying it works (there's a DTM test mode on the diagnostic reader that cycles it) and there's no need to replace it, unless its so gummed up you can't clean it, or the coil is burned out (never heard of this happening). also clean the throttle body, it can get remarkbly gummed up so it doesn't quite close all the way. I just take it out of the car and blast it with aerosol carb/throttle cleaner spray.

 

I know where the ECU is....what should I do with it Pierce? I have cleaned the TB off car along with the IAC, new according intake pipe, new FPR, neew Airbox T stat (I coulda wired it to the cold open position). THE CEL is not CEL it is the SERVICE light and it goes off 2mins after startup.

 

ooooh, the SERVICE light. ok, that just means the service light hasnt been reset in 5000 or 7000 miles or something (I forget the interval). in theory, its oil change and inspection time, but its only meaningful if your service guy knows to reset it each time he does the scheduled maintenance.

on my 92 740, there's a button behind a rubber cover just to the lower left of the speedometer, you pop off the rubber cover and use a pen or something to hold the button down for a couple seconds, and the light goes out. not sure if a 240 works the same or what. on other cars of similar vintage I've owned, its been everything from a red button in the engine compartment, to needing a dealer computer to reset, to some weird sequence of holding in 3 buttons at once, turning the key on and off twice, and tapdancing

 

I zipped around 2-3 miles today. Car seemed OK. When I stopped Idle was high...I let it idles for 5 mins...held high Idle even if revved. Put her in gear and went home. Driveway idle was near Groovy and there were no stumbles, or stall outs. Going for a longer ride tomorrow to see what shakes out. I dig this car. I just want to know how to get it dialed in. Zoot has improved a thousand fold since the day we met. Pierce do you think just crudded up injectors and rail would cause all of this and is slowly improving?(Hoping) I am down to half tank so I am going to run it down to see if it may be in tank pump related. I also need to change the plugs to Bosch or OE Volvo coppers. The ones we replaced the day I bought were champion coppers.