Hello,

I have a 1988 Volvo 740 gle wagon that 73,000 miles and I am experiencing issues with no acceleration (RPMs not exceeding 1500 rpms) when in drive or reverse. I have replaced cap and rotor, MAF sensor, TPS has been replaced, intake manifold gaskets have been checked, no apparent air leaks, and IAC valve has been swapped out, timing is good and fuel pumps have been checked and relay replaced. I can not seem to figure out what is causing this issue and after much research, I am still not able to find any suggestions. Is or has anybody else experienced this issue?

 

Off hand, I would say it sounds like a bad Crank position sensor but than when they go out you'll get a no start condition. I take it that you checked for codes even though have no check engine light?

 

88 is LH2.2, has no CEL or diag codes or crank positions sensor.

last engine I saw that would rev fine in neutral but had ZERO power in gear, the problem was a missing vacuum line on the ignition advance... but the bosch ignition in a 740 doesn't have any vacuum advance, its purely electronic controlled based on RPMs.

 

After looking through my notebooks of "weird problems and fixes" I found multiple entrees with this issue, came down to "blocked Cat" Easy to confirm just disconnect pipe from header.

 

73k miles? like new... i'd go for the plugged cat theory.

 

if you replace the cat, go for the california spec one, its going to last much longer than the cheap replacements.

 

I disconnected the cat from the exhaust and still no rpm acceleration in Drive or in Reverse.

 

One question, are the RPMs also limited in neutral ?

 

I think I would ohm meter test the idle switch on the throttle, make sure its not shorted/stuck closed. it should be open circuit as soon as the throttle comes off idle.

Is this a Bosch injection or Regina injection car ? Bosch uses a MAF (Mass Air Flow), Regina uses a MAP (Manifold Air Pressure) sensor.

 

also, I've seen a few cars, I don't know if the 740/940 is included, that if the engine thinks the tranmsission is in neutral, it will cut power way back to prevent overrevving.

question: with the engine off, if you put the shifter in D, and touch the starter, does it crank? if it does, your park-neutral switch is broken.

 

No, the RPMs are not limited in Neutral, they rev just fine.

Thanks, Pierce, I will give the idle switch a look at. As far as the injection, I have a Bosch with the MAF.

 

Ok!! you may have to rethink this issue, if it acted the same with the car in park then you have to reason that it's engine related but you now say it acts normal in park/neutral so my thinking it's the Transmission that's the issue.
If it were me I would jackup the rear end on jack stands and see if the "Trans" shifts as normal and also see if it is limited to 1500 RPMs in gear with the wheels off the ground.

 

I would only do that if you have VERY sturdy jack stands on a flat level hard (concrete) surface. you would NOT want the car to rock off the stands while you're spinning the wheels at road speeds!