Mismatched 1988 V10 Mismatched Suburban

[VileZambonie]

Have you tried unplugging the tcc solenoid and seeing what happens?

[MuddiGGEr25]

I dont have a locking TC, unless your referring to something else, I have a beefed up TH350, but i didnt get the lockup kind

[VileZambonie]

Sorry, and no offense but I didn't read the whole book.

Have you checked your exhaust back pressure? Is there a catalytic converter in place? Stock manifolds, single exhaust?

[MuddiGGEr25]

Sorry, and no offense but I didn't read the whole book.
its all good lol i didnt mean to come off offended im just really tired lol
Have you checked your exhaust back pressure? Is there a catalytic converter in place? Stock manifolds, single exhaust?
no cat, custom (from the date of engine swap) true duals but no H pipe which i think i will add later on, ive heard it runs a bit better with it, 2 oversized mufflers and one isnt very tight so that side has an exhaust leak, and both pipes are loose right where they come off the collector bc i tried to tighten them and i broke a bolt on each, but its not a bad leak.

[VileZambonie]

exhaust leak is far enough downstream to avoid interfering with O2?

[MuddiGGEr25]

exhaust leak is far enough downstream to avoid interfering with O2?

yes many many feet past the 02 sensor, but i had this issue before i tried tightening the exhaust also.

[VileZambonie]

If you are mechanically sound and verified, have no faulty inputs then what would your conclusion be?

[MuddiGGEr25]

If you are mechanically sound and verified, have no faulty inputs then what would your conclusion be?

Personally logic is pointing me towards either timing not working correctly for the engine build, or I still do not have enough fuel delivery, which i cannot verify either until later next week. I was getting alot of knock readings in that video i posted on youtube, but that could be a faulty knock sensor or a lot of real knock, but if i am getting knock because of a lean condition then I would have to make sure the FP is proper again, but also I am suspicious of one of my injectors because when i pulled them one at a time and put a NOID light instead, one injector was able to keep the engine running while the other injector could not when it was its turn for the test. I am fairly confident the timing advance components are all functioning properly, my input sensors have been tested and verified so i dont believe it is a sensor fault, with the exception of maybe the knock sensor, but I am not sure if a custom rebuild would have changed the "sounds" the knock sensor listens for and could be setting a false positive??? this is something i am not knowledgeable about.  I just ask on here because I am not familiar with chevy tbi too well, and dont really have the ability to chase leads that might take me nowhere, since i only get a couple hours before my back or knees act up and i have to call it quits for the day. I noticed during my drive earlier it almost seemed to sound like it wanted more fuel but wasnt getting it, it makes me wonder if the rebuild requires more FP or volume to accomplish its full powerband. I just want to get as close to 100% as possible before feb9th after that I will be upgrading the regulator spring and Fuel pump for sure, and maybe the injectors if i can squeeze it. I wish i had paid more attention to the TBI my uncle used to drive.

My next steps would be

FP test again
maybe find another used injector or 2 at the yard tomorrow if i have time
try another knock sensor?

[frotosride]

Custom rebuild? Any chance you have a gear drive timing set. This can very easily simulate knock and specifically says on most packaging and instalation instructions "not for EFI" and or ESP controlled vehicles.

[MuddiGGEr25]

Custom rebuild? Any chance you have a gear drive timing set. This can very easily simulate knock and specifically says on most packaging and instalation instructions "not for EFI" and or ESP controlled vehicles.

I would assume they were smarter than that, however I have 0 details on rebuild so far, waiting on a couple people that went hunting in this rig years back to see if i can backtrace the papertrail.

[MuddiGGEr25]

Update to original Topic:

I disconnected the knock sensor the same day my starter failed, it has been disconnected since then.

I feel underpowered, like it seems to drag itself along from 3500-6000rpm, but idle to 3500 seems pretty normal.

I can NOT get it to repeat the "turbo" effect from 2500-3500rpm, I have been trying for several days but to no avail.

I think my CEL is burnt out because it does not light up when KOEO, and it hasnt lit up since the knock sensor was unhooked. I have not connected a scanner yet to see if I do infact have a code.

I can currently cruise without it feeling like it wants to fall on itself 25-40mph.

also IMO i think the idle is high, but no vac leaks, ive even tried plugging all the ports with rubber plugs to eliminate possibilities. it sits around 900-1100 at idle, and even when up to 180F im still in the 900's.

I have seen a noticable in town MPG increase (1-3MPG) cannot give exact # because I havent refilled yet, but the tank is lasting longer, and I am not being any nicer to the throttle, I even went mudding a few days ago, and raced a jeep yesterday.

I am going to reconnect it later tonight and drive a couple days and see if the symptoms return.

I am wondering since the starter is right there, could the starter have been causing a false knock reading as it rattled around? it was pretty shot.

Also I am beginnning to suspect my used pump is getting tired, as I am almost always reading a lean condition, and I know a lean condition can lead to higher knock counts as well, I will get some free time towards the end of the week and test the FP again and see what i get. I am only wondering because it almost acts like its lean, and when i romp on it, it sounds like its sucking way too much air in comparison to the fuel coming in.

However what should be my next suspect if my knock counts remain high but my FP is actually ok? No VAC leaks, only minimal exhaust leaks, (less than 1/8th here and there) base timing is correct.

I have to tow a 25ft RV in a little over a week, so i need to be running as close to 100% as possible.

[VileZambonie]

pinch off the return line on the rubber fuel hose.

[MuddiGGEr25]

pinch off the return line on the rubber fuel hose.

I havent had it up in the air in a while, where does the steel go into rubber? is it up near the firewall, or above the tank?

[VileZambonie]

over the tank or up by the bellhousing. That line is steel braided so you will crush it. Go near the tank and pinch it off with needle nose vice grips.

[MuddiGGEr25]

sorry for the absence, I lost this thread in the 100+ bookmarks on this project.

I did get the 3/4 front and rear axles and spring packs installed (that has its own thread),

We did tow the RV home, it was 280ish miles each way, and 3,000lbs for the empty trailer on the way down, and 10,000+ with the motorhome on it.

We managed 55MPH average on the way back sitting over 13ft tall and 10,000lbs of trailer, and over 8,000lbs lbs of burb. we did 65-70 on the way down but had vibrations over 60mph because my ujoint straps were bent and cracked and i only had 2 bolts holding the driveshaft on, but it was too fricken cold and snowing to bother with it unless it broke, which I had the parts with me if it did, however this was remedied about 3 days ago because it was warm enough to crawl on the ground.

Learned that my peak TQ as the TBI runs right now is 3700RPM  I figured this out, when towing an RV on a deckover trailer weighing over 10,000lbs up a very very steep hill, well over a mile long, 3rd gear just couldn't keep me at 55MPH so I dropped to 2nd, throttle maybe 40-45% and although I couldn't go over 55MPH/3700RPM, there was more than enough TQ there to maintain it with ease. And cliffy was over 8,000lbs with full tank, almost every single tool I own and air compressor too.


Currently 4.10 Rear axle ratio, but if i get these 35's it will be 3.71, so we will see if that helps or makes it worse.

I am getting 10.8 mpg at 55mph with a good crosswind, and 6.9mpg doing 70-80 with no wind. the TBI is still sluggish at WOT when I need it most, but up to 75%ish throttle i have EXCELLENT response and power. So i am going to find that rubber line tomorrow and see if symptoms improve, if not ill actually bust out the FP guage at work on monday and see if i put a bad pump in.  long term goal was TBI pressure increase to 17psi, but i might be getting a 454 4bbl to put in cliffy later this month, and the 5.7L will go into the 81 motorhome, so I still need to figure this out, but once it goes into the RV it will have a inline adjustable FP, running off the ignition and oil circuits. so fuel delivery will not be a problem. and I will probably just regulate the TBI pump down to the 8-10PSI the BBC wants, I had a similar setup in my 77 RV when i got it.


I will also pull a plug or two tomorrow and see how they look. I sprayed throttle cleaner all over the engine, intake, every vac line, and no change in idle whatsoever, but my $12 tach says i'm idling at 850 in P and N, and R, D,2,1 I drop to 500-600. So i dont know whether to believe the SNAPON scan tool or the tach, the tach is showing accurate readings on the HWY when i punch them into a gear ratio calculator.

swapped a 150A 1 wire alt on, however the OEM 6" bolt snapped in the middle of SD at 1AM so I currently have a tiedown pulling the ALT tight until I can get the broken bit out of the block, which includes removing the fan and shroud.

based on crazy knock counts still, and the poor WOT performance im going to gander my issue is a fuel issue, add on that im always running lean according to the scan tool, AND im running 200F. But if i increase my fuel being delivered, im not sure im gonna like the MPG results lol, I might like the power though


Brake stall is 1500RPM, but does not overpower the brakes, flash stall comes very close to the same.