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Thread: TBI Issues
02-15-2011, 10:22 AM #1
I have a 1992 Chevrolet C/K1500. In 2004 I built a 383 and installed it. At that time I also switch to a 454 TBI and injectors. I had the chip reprogrammed for these changes and added a Walbro 255 lb hr fuel pump and adjustable FP regulator. The truck has never quite ran right. I have made a lot of changes and it has run better but it has always hesitated at WOT and would get hot stopped at a light in the summer. When it would get hot at the light the RPM's and oil pressure would rise and fall dramatically. I assume it is because I never installed a bigger radiator or electric fans. It became a non issue because I moved to an area where there were no red lights between work and home. I worked on the truck and settled because I put my money into my car.
I havenít had any problems until the past few months. While driving the truck I notice the RPMís would increase by about 400 but engine speed would not. With it being winter the truck never really gets hot but I also noticed it was not getting over 100 degrees. Also the truck would not start sometimes. I switched out my control module on the back of the distributor for the starting issue, which seemed to fix the not starting issues for the time being. For the RPM increase initially I checked the TPS sensor volts and they were low so I changed the switch. This started a whole evolution of issues.
The next day the idle was extremely high and white smoke was coming from the exhaust. It did not smell sweet like anti freeze but like the fuel was too rich. There was a faint ticking noise I could hear coming from inside the engine. I could hear it in the exhaust but it would get fairly loud from underneath the truck. I noticed my injectors were not flowing properly. I order some injectors and a gasket kit to rebuild the throttle body. I replaced all the gaskets and packings as well as the injectors. The engine would not fire with the new injectors (they were 350 injectors and I am programmed for 454 injectors). I put the old injectors back in and it started fine. I metered the new TPS sensor and it was at 6.5 volts (which I thought explained the high idle). I reinstalled the old sensor and moved it to get 5.65 volts. As for the truck not reaching temperature I changed the T-stat (I am programmed for a 160 T-stat) and started the truck. Everything seemed fine, temp went up, it idled fine, no white smoke and I couldnít hear a tick.
The next day I was driving to work and it reached 180 degrees and kept climbing. I ended up stopped at a light and it went up to about 220-240. As soon as I took of the temp dropped to 160 and stayed there. When I pulled up to the gym was idling high. In fact the speed limit was 35 and I let off the gas and the speed would not drop. As if it was on cruise control. When the speed limit dropped to 25 I hit the brakes and let off. The speed stared climbing on its own. After I was done at the gym I started the truck and the idle was low. It dropped so low that it almost shut off. I drove to work and the truck was coming back up to operating temp and shot up to 240 again. I shut it off. On my way home the temp shot up again but the idle seemed fine. But when I had to stop at the red light (I have those now) I could hear a faint noise almost sounded like a diesel engine.
I feel I may have to issues. For the idle maybe a chip or sensor problem but for the overheating and ticking I feel I have a lifter going bad and a blown head gasket. This is my daily driver but I am getting so close on the car so if the truck can hold out for maybe a month I can use the car until I go on deployment.
I have been talking to Sean at TBIPARTS.com and he has been helpful. He is also sending the correct 454 injectors and a new IAC motor. Any additional information anyone can offer would be great.
02-15-2011, 10:35 AM #2
Have you considered a TBI kit like Holley? They are specifically made for larger engines, and probably won't flood the truck out causing hesitation at WOT. It seems that quite a few people have these problems when they go with the 454 TBI. Good luck!Jess
02-15-2011, 02:37 PM #3
I am in it too deep to switch to a Holley setup. My chip is programmed and I ordered injectors. Besides if the motor blows I am ditching the whole thing and switching to a 5.3 or 6.0 Gen III/IV.
02-15-2011, 03:57 PM #4
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- Sep 2010
- Far West, Oregon USA,
- Blog Entries
I agree Wayne, you have 2 different problems here but your wide variation in temperature could be adding to part of your running problem because of the diff readings your ts is sending to your ECU. I'm wondering about your 160 F thermostat. I also didn't know that you could program for a 160 T stat. Have you tried a 195-200 F stat? I know you probably chose the 160 F for more HP, but I think this may be some of your idle/running issues, & wide variation in RPMs.
For the possible head gasket check, are you seeing any bubbles in the radiator? Have you checked the compression? If you do have a HG blown you should be using water, & there was a point where you said you were getting white smoke out the tailpipe. You said it smelled rich, but rich mixture gives you black smoke, & a coolant leak gives you white smoke. I'm not sure how a HG leak could seal itself up unless you retorqued the heads, or put some sealer in the cooling system ?? I would pull the plugs & see if any of them look like they've been steam cleaned, or if there are any water drops on any of them. If you do have a HG problem you should address this first cuz your running problems would be greatly affected by the coolant in your exhaust skewing your 02 sensors.
Last edited by stephan; 02-15-2011 at 03:59 PM.1988 Chevy C-3500 2wd (no pic)
350 c.i. 5.7 L Stock Block, 4 Bolt Mains
L-31 Vortec Heads, Edelbrock Cam & Intake,
Holley 650, Flowtech Headers, Magnaflow exh.
Jet Trans 700R4, B&M Ratchet, 4:10 gears,
3" susp. lift kit "shadetree"
No rev limiter, No speed limiter lol
02-16-2011, 08:17 AM #5
Yeah, I am going to check the spark plugs this morning. I will check compression if I have time, the overheating got me this morning. I was driving to work and temp reached 230 but never dropped. It got up to 250 and I pulled off the road. I popped the hood and could hear the anitfreeze running down into the motor. I waited a while and started the truck and it hovered around 210 and then dropped like a rock to 100 and never came back up. Guess the fail safe worked but the thermostat did not. NAPA only has a 180 so I will try that. I have been afraid the whole time it is a head gasket but if it is I am in a world of the not so good stuff. Work is insane right now and I have a 71 Camaro I am so close to finishing. Maybe I can milk it by retorqueing heads and add a sealer. I know if I pull the heads I will find more wrong and then you know how that spirals out of control. Keep you posted.
02-16-2011, 03:05 PM #6
Well, I changed the Thermostat again after the other stuck open. This time I used a 180 but before I finished up I checked some other things. I did not pull all the spark plugs (2 of them are a pain to get to due to the JBA headers). The six plugs I pulled looked fine, a little used with light build up but nothing out of the ordinary. Pulled the valve covers to check the oil (I may change the oil to get a good look at it but I just changed oil and oil is expensive) and no sign of antifreeze or discoloration in the oil. I installed the new 180 and drove down the road and it heated up to about 220 and stayed there as I drove home. When I pulled into the driveway (total trip of about 6 miles) the temp dropped fast to 180. I have an infrared thermometer and I waited for the truck to cool so I could check it when it heated up to 220 again. This time it was idling low enough it wanted to shut off so I had to drive it. When I drove down the street it got up to 210 and I turned around to head back to the house. As I was going to pull over to check the temp it dropped to 180 again and stayed. So after stopping at the house I went to work and it heated up again, this time I caught it in time to take the temp. The truck dash read 210 but the upper radiator hose read 160 to 176. The thermostat housing read 180. I measured the area of the block around the temp sending unit to the dash and it said 195/209 but I imagine I was picking up a lot of heat from the headers.
By the way, from time to time over the years a little white smoke would come out of the truck in the winter until I upped the fuel pressure. When the white smoke poured out of it this time I had just added Marvel Mystery Oil to the truck the day before (never used the stuff before) and I was idling real high. It did it again later that night and once more yesterday morning while warming up. It was early in the morning yesterday and it was cold. Besides that it does not have white smoke coming out all the time and never while driving (in fact, it is black when driving). You can smell the fuel when it is smoking and no sweet antifreeze smell. Besides, when all the bad smoking was happening I had not changed the thermostat yet and when I went to change the thermostat and open the radiator it was full all the way to the top. I figure if it was a head gasket there would be smoke all the time, it would overheat all the time (not just when temperature rises initially) and it would lose antifreeze.
Right now I am starting to lean toward the sending unit for the dash gauge between the 1 and 3 cylinders. Probably inexpensive so I will pick one up on the way home. After that it may be headed for a mechanic if no one else has any ideas.
02-17-2011, 12:33 PM #7
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- May 2010
- Central IL
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get a scanner and see what the computer is reading for coolant temp. There are 2 different sensors on the engine, one for the gauge, and one for the computer. if they're both reading the same, it's not a sending unit problem.1986 Chevy G20 Tow Rig - 5.7 TBI conversion
1978 Mustang II King Cobra Road Racer - Holley 650, MSD 6AL, 5 speed, 10 point Roll Cage, 9" posi, fuel cell, custom interior.
02-18-2011, 06:52 AM #8
Temp is different between the sending unit (the one between the 1 and 3 cylinders) and the CTS (the one on the manifold besides the thermostat housing). I have an infrared gauge and it reads 209 to 220 (which the gauge in the truck reads) on the sending unit but up at the thermostat it reads about 160-190 which in range with the thermostat. Everything is starting to point to either a water pump not flowing well (or at all) or the lower radiator hose it collapsing on itself. From what I can tell there is no circulation and basically the motor has to get hot from the bottom up. It shows because around the sending unit it will be hot but at the upper radiator house it is 160. I believe once the hot temp reaches the thermostat and it opens the system re pressurizes and the circulation works somewhat right. Once the thermostat opens the first time it is fine and maintains temperature. I have a water pump at the house and I am going to change the lower hose. Probably flush the system as well.
Last edited by wayne76; 02-20-2011 at 08:07 AM.
02-20-2011, 08:05 AM #9
I spent all day on the truck yesterday. I drained all the coolant and pulled the radiator. I flush the engine out from top to bottom. I had the knock sensor out and coolant plug. Water pump was off and thermostat as well. I took the water pump cover off and I saw nothing that would indicate any issues. After I was done flushing the engine I drilled 2 holes in the thermostat and changed the sending unit to the gauge cluster, as well as, changed the lower radiator hose. I clean everything up and filled it up with water. I left the cap off and watched for circulation and it seemed fine. Topped it off with water and drove it to work this morning. Temp never rose above 200 and the thermostat opened. I figure if it continues to run right I will drain the water from the radiator and fill it with antifreeze and let it roll on.
I did notice there was an orange/brown tint to the antifreeze but clean otherwise. The antifreeze has been in there since 2007 but normally a brown tint would indicate that exhaust is pushing into the coolant thus a head gasket issue (probably explain the bubbling I hear coming from the heater core from time to time). I am not loosing coolant so until the car is done I will let it go. I may change head gaskets then but I really want to put a Duramax in the truck. I also changed the injectors and everything seems to be running better and a slight power increase.
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