89 740 turbo - sputters and pops when accelerating

jessek · Post by **jessek** » 04 May 2011, 12:34

OK, so I'm a new guy when it comes to these volvo things. So the car will start fine idle fine at about 800 to 1000 rpm. it will even accelerate ok at a slow pace. but when i get to about 40-50% throttle it will sputter, pop, and miss. When i floor it it will go back to running pretty well once it spools up. Could this be because the MAF sensor is jacked and is causing the ECU to make bad fuel inputs on the map between idle and WOT? Is that even how it happens on these cars? I've got alot of experience with fox body mustangs so I'm trying to apply it here. I put 92 octane and fuel system cleaner in it and no change. I have read about people cleaning the MAF sensor so i think thats the next step. I've done alot of searches here and elsewhere to no avail. hoping somone else has had this problem and its an easy fix [fingers crossed]. Thanks in advance

Jesse

Post by **billofdurham** » 05 May 2011, 12:24

Welcome to Matthew's Volvo Site.

volvo things

Hmmm!

Try disconnecting the MAF sensor. This puts the car into limp home mode. If the symptoms are the same then it is a possible MAF problem. MAF cleaner is relatively cheap and won't do any harm.

Other things to check:

All earth (ground) connections on the intake manifold and from the engine to the chassis.

The MAF connector for loose terminals.

The radio suppression relay. On the turbo model this is on the driver's side strut turret. It is actually a fuel injection relay put into the system to prevent radio interference. If it is faulty it can play havoc iwth the FI system. The cooling fan relay is next to it and they are interchangeable so you can tets this one quite easily.

The air filter box has a thermostatically controlled air flap which changes the air flow direction as the engine temperature varies. On cold days the flap directs warm air from the exhaust manifold and as the temp rises the flap should move to allow a flow of air through the intake onb the box. This thermostat is prone to failure and usually leaves the flap on the warm air setting. This can cause the MAF to give false readings and, in extreme cases, cause the MAF to fail.

Knock sensor.

There is more but this is a start.

Bill.

jessek · Post by **jessek** » 16 May 2011, 17:03

thanks for the input. Ill try those things.. I cleaned the MAF but it didnt help. Ill disconnect it now.

jesse

jessek · Post by **jessek** » 17 May 2011, 12:07

OK so i disconnected the MAF sensor at idle and the rpm's began to surge and hunt. when i plugged it back in it went back to normal.. does that mean the MAF sensor is still good?

jessek · Post by **jessek** » 17 May 2011, 12:39

When i turn on the ignition should i be hearing a fuel pump kick on? I've read that i should but i don't on this car.

jessek · Post by **jessek** » 27 May 2011, 12:14

OK so i found the fuse for both fuel pumps. I pulled the fuse for the exterior pump and it was hot with ignition off. The fuse for the in-tank pump was hot with the engine on. When i pulled the exterior fuse the car would not start. When i pulled the fuse or the in-tank, the car started and ran the same as with installed. So, does this help to diagnose the problem? could the fuel pump relay still be an issue or does my car run like crap due to the in-tank pump not working? I also still do not hear any pump run when i turn on the ignition. thanks

Jesse

jessek · Post by **jessek** » 27 May 2011, 12:20

CORRECTION: looks like the fuse for the external pump is also the fuse for the engine control so makes sense it wont start with that one pulled. still figuring out where and how to check the relays.

Post by **billofdurham** » 27 May 2011, 15:17

Neither pump will run continuously whist the engine isn't running. When you switch on you should hear both pumps momentarily.
The fuel injection relay is in the fuse/relay board behind the front ash tray, at position E in the attached. To access relays, remove the ashtray by pushing the spring clip at the top and the fuse panel cover by pushing the plastic snap at the bottom. Remove the snap-on cover over the cigarette lighter with your fingernail or a small screwdriver. Remove the two Philips screws securing the storage box. One of these is angled in. Remove the storage box by gently tugging on the left side, pulling it and the cigar lighter wire out from the console. Beneath it you will see the relay tray behind the fuses.

740 fuse_relay board.pdf: (335.29 KiB) Downloaded 336 times

Put your finger on top of the relay and switch on the ignition. You should feel a click if the relay is working.

Bill.

jessek · Post by **jessek** » 28 May 2011, 00:31

Thanks to the replies on here I found and tested the relay. it seems to be working. Also, I jumped the power to the pumps without the relay and they came on. not sure what the fuel pressure was or what its supposed to be. So I went ahead and pulled the fuel filter cause its a 15$ part and i figured what the hell, and of course broke the line from the pump to the filter. Ordering a new one from IPD. The banjo fitting is stuck on the input end of the filter so i need the bolt also. 78 from the dealer. I think im going to check the throttle position sensor/throttle body voltage while i wait for the part.

jessek · Post by **jessek** » 28 Jun 2011, 16:05

Well fuel filter changed and still the same problem... I cant figure out how to get a fuel pressure regulator on it either. Anyone want a 89 volvo turbo?