Bogs at wot

[phule]

Bear with me I'm frustrated and needs someone else opinion. This is a long story


Vehicle: 1988 c1500 305 Tbi
Mods: open element k&n l, long tubes with h-pipe dual muffed single exit no cats.

Couple months ago I seafoamed my throttle body. When I was done I reved it a couple of times smoke etc. Went to go leave got on the road punched it and it falls on its face sometimes it clears up. Figured a blew out some plugs no big deal. Throw those in no change all plugs looked the same had a light white coating wich i figured as running lean hence the fuel diag. Buy a fuel pressure gauge I have the low side of 10.5 I dead head the pump pressure doesn't change. Ok bad pump replace pump and line retest. 11 psi at idle deadhead pressure rises ok:thumbup:. Take for a drive same problem. Detest fuel pressure fuel pressure drops of at wot. Ok looking at a regulator. Well I replaced that tonight it no longer backfires through the intake and has more pickup but above half throttle there's nothing. Looking for help not sure what direction to go now.

 

[jdyates]

Bare with me, im on my iPod lol. first off, Do the paperclip scan. Im gonna assume you have a TBI. Jump the ALDL terminals and see if your truck has any codes. If so, let us know. If not, you can try checking your O2 voltage, first of all. Bad o2 sensor will cause problems, maybe the seafoam screwed with it (supposedly o2 friendly, but who knows?). Then move on to checking all the vacuum lines. Theres 3 coming off the throttle body, make sure none have cracks and are fully hooked up. Check the TPS, if bad, wont send the correct throttle readings and the truck wont pour in the necessary fuel.

Then you want to move on to spark. You said you replaced the plugs, now check the plug wires for arcing (super easy, just turn the truck on at night and take the bulb out of the underhood light and watch for arcs across the headers, etc), then you want to pop off the distributor and check all the terminals inside, the rotor blade, and make damn sure theres no moisture under the cap.

This problem started randomly so im going to assume the timing is fine, but i definitely couldnt hurt to check it.

After all that, i would take the whole throttle body off and clean it manually. You would not believe the amount of buildup that could be in the vacuum passages at any given time. Just rip it apart and soak i in brake cleaner, sscrape off any buildup as necessary, and us a small flathead to scrape the insides of the vacuum passages

Sorry for any spelling errors, etc. this touchscreen is a pain in the ass. Thats all i got off the top of my head wihout any data. Its pretty hard to diagnose stuff like this without the truck being in front of me, these problems could be anything, or be as simple as a ground wire.

 

[phule]

I did check timing its good.
Wires are msd approx 2-3 years old less than10k miles
Same for cap and rotor but I will pull of tonight and double check
Ill try sensor checks later this week.

 

[jdyates]

The thing with these TBIs is that if there is any hiccup in the spark or fuel, nothing works right. You covered the fuel system, so it makes sense to check vacuum and spark next. They are very sensitive to cross-firing in the wires, so we want to chrck that they arent touching the manifold or are too close together. My truck started bogging down BAD one day, couldnt figure it out. A few hours later, when it was dark, i popped the hood on the side of the road and sure enough, there was a tiny crack in the plug wire boot of cylinder #3 arcing across the manifold. It could benjust a coincedence and have nothing to do with the seafoam, which is why i like to check everything.

 

[oohunter04oo]

My 94 was doing some crazy things when the coil went out. I had spark but it wasn't enough. Also make fuel your fuel filter isn't clogged, or air filter or exhaust. Maybe a plugged catalytic converter, best way to check that is remove the O2 sensor and run the truck and see if it clears up.

 

[phule]

I'm gonna check for arcing wires tonight after it gets dark.
(Also added vehicle info to post 1)
I did the fuel filter a few years ago I almost want to throws in a new one because it does sit so much.

 

[phule]

Alright gentlemen, time for an update with the verus at work checked some things real quick on lunch.
1. No codes
2. Tps is within parameters and is cyclung evenly
3. O2 is cycling evenly around 430mv at idle and does climb with throttle
3. Coolant temp sensor appears to be working well
4. Map sensor is reading but forgot to record data (doh)
My one area of concern is I unplugged my knoxk sensor because one of my long tubes hits the frame and I think it was picking it up point if that story it was reading 198 coubts rock steady. But thats has been unhooked for 3 years and no issue

 

[phule]

Also its raining tonight so im gonna check for arcing when I get outta work

 

[phule]

Update no visible arcing when I got out of work last night.

 

[phule]

Well just to bump my thread I'm gonna pull the throttle body today and give it a good cleaning. Also I'm gonna check my cap and rotor.