Have you checked fuel pressure (50-60psi) and that it holds ? These pumps and injection systems are notorious for problems.

 

That is pretty much the last thing on my list of suspects. I just cleaned out the EGR valve and replaced that gasket. I'm trying to find a FLAPS in the area that has a tester I can rent.

 

Walmart.com: Equus 3640 Innova Professional Fuel Injection Pressure Tester: Automotive I got this one and it works fine for not alot of bread.

 

Hooked up a scan tool with live data and found out my timing was advanced by 20 degrees...got it down to about 6 and it runs much better. Still a VERY SLIGHT stumble at idle, but I feel like I got a ton of low RPM back so I'm happy at the moment until I get get in and fix everything completely.

 

What about your throttle position censer that usually affects the truck on soft acceleration. My truck use to do something very similar anyway that's what it ended up being .And trust me it is cheaper to take it to a shop than it is to just guess. I have learned this lesson the hard way.

 

I'm fairly good friends with the owner of a reputable chain of auto repair shops in the area, only problem is, due to work I can only stop by their shops on Saturday's and they are ALWAYS packed solid. I will definitely look into the TPS this week once I get paid. I will report back if anything changes.

 

@Billfrank85,

I am having a very similar problem with my truck and did just about everything you did:

cap/rotor
wires/plugs
cleaned MAF
replaced MAP sensor
replaced TPS
fuel treatments
cleaned throttle body

and a few other things....my question to you is what did you do to correct the timing issue? I am starting to wonder if that is the issue with my truck. I noticed a slight improvement with the cleaning of the TB, but I still have some sluggishness and also have some stumbling and wacky shifting. Would like to look into this possibility.


Thank you

 

Go somewhere that has a scan tool with live data that shows your spark timing (retard or advanced) if it's advanced you need to move your distributor counter clockwise I believe and if it's the opposite move it clockwise. We just moved it until I was at around 6 degrees advanced instead of 20...pretty noticeable improvement for me, anyway.

 

Rotating the distributor adjusts camshaft retard. It calibrates the camshaft position sensor to the camshaft. Much like the crankshaft position sensor relearn procedure calibrates the crankshaft position sensor to the crankshaft. Injector timing, injector pulse width, ignition timing, misfire detection, (and many other things) are all based on data from these two sensors. The PCM is a computer, if you put junk data in, you're gonna get junk out. Both sensors must be calibrated correctly. The "ignition timing" that you see on the scan tool, is how much advance the PCM is applying. Assuming camshaft retard is correct, if you rotate the distributor, you are limiting the maximum amount of advance the PCM can apply, (along with a ton of other stuff). With the engine at idle, at normal operating temperature, in closed loop operation, trans in park or neutral, all accessories off, ignition timing should be 21 degrees. Do not try to adjust camshaft retard strictly by ignition timing. It is not a "backwards compatible" adjustment. It requires a capable scan tool to adjust it correctly. At 2,000 RPM, camshaft retard spec is zero degrees + or- 2 degrees. If you're showing 6 degrees of advance on your scan tool, camshaft retard is off substantially. If camshaft retard is off more than ~27 degrees, P1345 will set and the SES light will come on.

Once camshaft retard is back where it should be, check fuel pressure and leakdown. On your 1998 CSFI system: Key ON, engine OFF, fuel pump running, pressure must be 60psi to 66psi and must remain above 55psi for at least 10 minutes. This should be the FIRST thing you check when you have a driveability issue.

 

Crap. Well, I don't know what my camshaft retard is and I won't be able to get scanned again until next Saturday. I don't have P1345 anymore and my truck seems to be running better. What are the consequences of running like this another week, with my camshaft retard probably being off and my ignition timing not to spec?