Guys I have a 1988 740 Wagon with a B230FT. I have a been battling this gremlin for about 5 months now. "Tech" a very helpful member on this site has been helping me along the way but I though I would post this for others to bat this problem around.

I'm having random misfiring, sometimes way worse than others, then at times it never misfires?? Usually a couple blips of the throttle clear the misfire up, then it comes back usually when I put the car in Drive or Reverse. Misfiring doesn't occur in the mid-range though. So weird!
I can recreate the "misfiring sound" by unplugging an injector plug. It Sounds just like That.

Also another issue is...I can't give my car more than half throttle or it starts bucking and missing then will pickup with full power then back to bucking and missing again. Almost like it occurs when the car is under boost at more than half throttle. (This issue is not random, it happens every time I run the car.)

So far I have checked or replaced on my 88 740 230FT...

Cap and rotor w/plugwires and Spark Plug's
ECU
O2 Sensor sweeps between .3-.9 Volts
Fuel filter
Ran a bottle of Chevron Fuel system cleaner
MAF Sensor
Knock Sensor
FPR- Fuel pressure regulator
Fule Pump Relay
Ignintion control Module
New Timing Belt
rear main seal
intake manifold gasket
Cleaned Throttle body and Idle control module and swapped out for another Idle control module.

Any suggestions guys? Maybe new....
Coolant temp sensor
air cleaner
fuel pumps- maybe weak fuel pressure to the fuel rail? Don't have a fuel pressure gauge to diagnose this though.
Timing off for some reason?
maybe a broken ground wire or something?


ahh.... this things driving me nuts!! haha!

Any Help would be greatly appreciated!

-Thanks guys!!

 

Assuming the check engine light is on, and you have pulled the codes (assuming that car should have a code reader)?

How many miles on the car? (Spark plug gaps ~30)
It sounds like the MAF is cutting out, but it is probably a fuel issue. Was the AMM replaced or just checked?
The injectors might still be clogged. I would look into rebuilding them. The pumps might be bad, but you should test the pressure before replacing.

The forum just got updated, and some people might still be having a hard time logging in. So you will get a better response from them

 

TIPSP- Thanks for the quick reply!

Now, I don't think my car has a check engine light. Well it's never been on at least. If it has one it must be burned out. I was told my year of car that you couldn't plug it into a code reader?

The car has 170,000 but I just put a 88 B230FT out of a parts car in it. All i know is the motor had about 60,000 miles on it. The motor was gone through by a local volvo dealership and the Timing belt was replaced. Everything else checked out fine.

As for the new plugs.. I didn't gap them. So I'll pull them out tomorrow and have them gaped. Good point!


Now the AMM was just check by unplugging it while the car was running crappy, but that seemed to make it run worse. It was backfiring and wouldn't really idle. Now I do have a parts 88 740 Turbo. So I might pull out the AMM and try swapping it out and see if that makes a difference.

I'll get that fuel pressure checked ASAP that way I can eliminate at least a couple ideas.

A clogged injector is what I was thinking too TIPSP! But why would it be so intermittent? Should it be just clogged or not clogged?
Now how do I go about rebuilding my injectors? Could it be done myself or just have them sent off to have it done?

Thank you for you help!

 

My 1991 740 does the same thing. I have been looking at injectors also. Brickboard has a section on do it yourself injector cleaning that i am going to ty this weekend will post if it helps (i hope so do not want to chase a wiring problem!). There also companies you can send them off to and get them cleaned and calibrated, if you have a set of extras that might be the way to go. I am not that lucky and cannot do without car for 2 weeks. Good luck Cobra!!!

 

I'm in the middle of diagnosing a similar situation in my '85 250 wagon. Its in another thread. So far, I've pulled the plug on the AMM and attempted to drive the car, but it won't come off idle without stalling.

 

I believe in 88 volvo started putting OBD1 in the cars, so some might have it and some wont (i am not sure on this thought?).
Now.....Was the car a B230F from the factory, and you swapped in the B230FT, or was it a turbo from factory and you just replaced the motor? How long ago was the swap, was it before or after this "5 month" problem?
If it was an NA car and you just swapped motors, You might have to swap the wire harness from a turbo model.
I would try a different AMM, form a turbo, for starters, then also get the pressure checked. My dad got my injectors rebuilt, but I dont remember where.
For the injectors...Even if you add fuel cleaner, there will still be old vapors that build up. I believe RC Engineering (Click Here), can rebuild, blueprint, flow bench...etc., but as the previous poster said that you will have to send them in.
Or depending on how much it will cost to get them rebuilt you could get new ones (well rebuilt) from Here (Click Here). BrickBoard is a great site.
This is also a really good site to help self diagnosing (Click Here), which I think is built from the brickboard QanA. Another good site that get metioned is Step by Step.

There are some smart people here (like tedv, blue goose, cbevis, bubba240...etc.), but they arent loggin in yet, so I would wait for their opinons.

Good Luck!

 

Three out of four of my Bougicord spark plug wires on my 1987 740T were essentially dead. Couldn't get a resistance reading on them and couldn't get a light from them using the timing light's inductive pickup. Still, the engine ran, it seemed, on 3 cylinders. I was amazed.

Also, when I first got my 740, it would slow way down and blow black smoke going up small hills. Turned out to be the air filter.

 

A little "Update" guys!

I started up the 740 today after work and it was running on 3 cylinders. So I opened the hood and started unplugging fuel injectors one by one. The first 2 almost made the car stall. Then when I got to the third cylinder I unplugged the injector and it didn't make a difference on how the car ran at all!
I may have narrowed it down to one cylinder at least. Lets hope! I have 8 extra injectors kicking around so I'll try swapping one out and see what happens. If that doesn't work then I may have electrical problems?

TIPSP- It is a factory B230FT car. So I swapped for another B230FT. My mom ran the car out of water and warped the head so I scrapped the motor and put in a different one. The swap was about a year ago but I lost interest up until 5 months ago. So the problems have been with the car since day one.

Thanks for the help guys! The response time is amazing on here!!

 

Cool! Hope it all works out for you!

And since you have so many injectors, you wont need to get them rebuilt

 

Make sure the wires and plugs are good as well.

 

I will do that tech, Going to go swap out that injector now and check plugs and wires. Thanks tech!

 

Ok we will be waiting to hear back from you.

 

Ok! Drum roll please......................

My problem was a Faulty Cap on the distributor!!!! And It was new! So I ruled it out! What the heck!!! I put an old crummy cap on as a last resort. And what do you know, it worked! Figures,the last thing I check. 5 months wasted haha.

Thank you ALL that have helped me along the way. I have a RUNNING 740!!! I'm sure I'll need you guys again sometime. I'll try and provide some of the knowledge I have gained also. Thanks again!


This is the "NEW" Faulty distributor cap.........There is a chip out of the inside about the size of a small pill. Wouldn't think that small of a chip would cause all the issues I was having? Got me!

 

Awesomw Cobra,hope you get many miles of enjoyment out of your 740. The complements to the people that responded where pleasant to see. Good luck with your BRICK.

 

Congrats man glad all is well now!!!

 

gforce- No problem man. If it wasn't for guys like you the car would have been gone a long time ago.
Hey, keep us posted on how your progress of your car is going. Well get that fixed up for ya! Good luck!

tech- Thank you! It always helps having a Volvo tech on here. lol!