I'm servicing my friend's 1989 truck for her since she's letting me borrow it and I'm doing some routine maintenance. Spark plugs and wires were replaced last year and all fluid levels are good to go. It was running great until the other day when it just started missing at idle and acceleration. I re-checked all the plug wires and plugs and they are in great condition. I even replaced a cracked PCV hose and reconnected another one as well that was loose, but it didn't help. It appears to be like the spark and/or fuel is just cutting out. The spark plugs were all fine (no signs of fuel saturation due to missing spark) and I'm just not sure what to do/check next.

Under part throttle acceleration it misses and bucks pretty badly at times, but when I floor it while it's happening, it appears to go away.

Any suggestions? I'd really like to fix this for her. Thanks!

 

Could be an EGR going, check the codes see what pops up. when the EGR gave out on my '95, it felt like it was losing fuel, but a simple code read put that fear to rest, EGR will be code 32, I believe the '89's will let you read 'em. If not the EGR, could be the fuel pump, it's common on these to go out, or injector/carb issue (not sure if '89 is carbed or TBI)

 

I get the following set of CEL flashes when I do the key switch on/off 3 times...

1 2 3 4 3 3 1 5 5 5

 

You can find this link in the FAQ in this section. https://dodgeforum.com/forum/general-tech/8717-service-engine-codes-for-obd-engines.html
Before you fix anything dubble and tripple check it. Disconnect the battery, for a few mins. then reconnect. This will rest the comp. Then run the truck up to temp and see which ones come back on.

You have code 12, 34, 33, 15, 55

12 Direct battery input to PCM was disconnected within the last 50 key-on cycle(Normal)
34 Speed control Solenoid circuits
33 A/C clutch relay circuit
15 No vehicle speed sensor signal
55 End of error messages

 

How do all those tie in to each other? It seems like a bunch of random codes that would/could be set off by only one real (electrical) problem. I just have to figure out what that is.

Any guesses just based off these codes?

 

Any ideas? I would lean toward it being the speed sensor since there are two error messages for those. However, how would that make the car miss at idle? That doesn't make sense to me. Or, even if it was the AC clutch relay circuit. Nothing is adding up here to the car missing, hesitating, and randomly cutting out.

 

Did you rest the computer like I sugested. Sometimes it will save the code for 3-4months or more. So If one connection had some water in it at one time that cased a code it will still be there. SO its always good to reset the comp. Then run the truck and recheck the codes.

 

I did unhook the battery for about a half hour then reconnected it back. It is still throwing codes but it appeared as if they may be different than before. I'll have to run it up to temp tomorrow and check again.

 

Just replaced the fuel filter and it seemed to get rid of 90% of it. It still has some random hiccups. Is this expected when just replacing the filter?

 

Oops, never mind. It's back to missing and hesitating again.

The weird thing now is, at idle it runs perfectly smooth. I revved it through all the RPM's and it's smooth as can be. HOWEVER, once I put it into drive, it starts running like crap.

What's going on here?