I posted on the engine forum and got no help at all so I figured I'd try here. I have an 88 with the 4.9 inline six. I've changed the plugs, wires, Dist. cap, fuel filt., air filt., oil & oil filt, pcv valve, and ran sea foam. Did some other stuff too but not important at this time. Its still missing and driving me nuts. When I start it cold it runs great, once I get to full operating temp. the problem starts. As soon as I sit at idle or drive slow it will miss in first and second gear. Once I get a little speed and airflow going it quits. I'm assuming something is getting hot. I'm leaning towards the coil, dist., or the timing. I really hope it's not all this magical emmisions stuff that I read you guys talk about all the time!

Thanks in advance!

 

You seem to have covered just about everything. However I would be inclined to try a coil and after that do a compression check.

 

well as it gets worse as warms up i would try coil and tfi as they are not too expencive

 

Thanks guys. The coil is what I was leaning toward. I guess I just wanted to hear it from someone else or find out if anybody a test of somesort.

 

Before you throw money and new parts in your truck, check for codes. You can go nuts trying to guess which part is failing.

 

I agree lv2race but I'll admit I'm a little intimedated by the whole codes/computer thing. It's funny pulling a tranny doesn't even phase me, but god forbid I do anything electrical! The check engine light flashes at high RPM but never stays on constant. I bought this truck used and it had been somewhat negleted so all I've done so far was happening no matter what. I was hoping I'd get her running right along the way. Guess not so, now I'm starting to fish for answers.

 

check codes or take it somewhere to have them read.

do not be afraid. it is a simple process.

 

There you go then.. the computer is seeing a problem and is just dying to tell you, but you're afraid to ask for some reason. Pull the codes and stop smashing your head against the proverbial fender. It'll be the easiest thing you'll ever do on a truck, I promise.

 

I have an Actron CP9015 that cost me less than $35. There are some posts here that tell you to use a paper clip, but I already have the code reader. It takes no time at all to scan for codes and it is one of the best tools I have ever bought.

 

Start by checking the codes as the other guys have mentioned. Most code readers come with a manual so it really isnt that hard. Once you get the hang of it you will wonder what the fuss was about.

 

OK I went out and got the code reader and ran it. In the engine off key on test I got the codes 32 and 29; in the engine on test I got the codes 42 and 32. This is good but don't know where to go from here.....HELP!

 

Code 32 has to do with the egr. Remove the egr valve and clean it as the carbon may be plugging it up. Check the wiring connector to the evp which is on top of the egr and has a wiring connector attatched to it.With the connector disconnected , on the vehicle side of the connector , with a digital multimeter check for around 5 volts at the orange-white (power) and black - white (ground) at the connector.There is a vacuum hose to this sensor also. Make sure it is not cracked or broken. Test the evp(egr valve position) with a vacuum pump and it should hold at least 10 inches of vacuum.You should also see the pintle go up and down as vacuum is applied and released. When running the koeo test remove the vacuum hose that is on the evp and attatched a vacuum gauge to it. At some point during the test the gauge should show vacuum and then drop off. This would indicate the the evr (egr vacuum regulator ) is functioning properly and vacuum is getting to the valve.
Code 29 is the vss(vehicle speed sensor) Check the connector at the transmission for dirt or corrosion.I have no experience with that sensor so that is really all I can offer on that one.
The code 42 indicates the the O2 sensor is not switching properly. If this sensor is several years old or you have never changed it it would probably be a good idea to change it. Its your call.

 

Does anyone have a picture of the EGR valve? I'm pretty sure I know where it is but the picture in the manual isn't the best. Thanks for the help guys.

 

did a search and found it. Thanks.

 

I don't have a multi-meter (leaving to get one now) so for giggles I disconnected the EVP and ran the truck. It did the same thing ran great until it got warm and then started missing. I can't sense (with my finger) any vacuum on the line it seems to be in good condition. egr valve looks to be fun to remove the nut going to the exhaust input is rusted solid!