Quick couple of questions: Did you change/check your thermostat? Do you have an infrared thermometer? What’s your fuel pressure?

 

I've been working on engineS since I was 11 years old can you explain to me how a thermostat can make a engine rough run rough in the 1st few minutes of operation? I am from the midwest so I know cold.

 

The previous owner said he just put a 195* thermostat in and appears to be working fine. I used an Infrared thermometer on the radiator, thermostat neck, etc and it agreed with guage temperatures. The truck heats up and stays at 210*. Doesn't matter if you are going uphill or idling in town. It heats up and stays at 210*. I have no idea what the fuel pressure is. There isn't a port to plug a guage in the line and I don't have anything to fit into the line. I did replace parts in the fuel pressure side of the TBI when I rebuilt it. I can't get the truck to a garage because I can't keep it running. I don't mind working on it but it is going to be -12 tomorrow and I am not sure what to do anyway. I guess I could buy some kind of fitting to put in the incoming fuel line and then get a gauge but that will be a few days.

 

 

Ok, temp is not the issue. Temp sensor could be. I would take a resistor reading across the terminals, disconnect the plug, when it’s cold and when it’s hot just to make sure it’s changing.

The only way to measure fuel pressure is with a TBI fuel pressure test kit. You might be able to rent one/loan a tool from the chain parts store. It is downright cold right now.

 

Keys here we go again, I've been working on engine since I was 11 years old, tell me why you think the only way to check fuel pressure Is with some type of after market gauge? In a pinch you can use a tire gauge, but you have to solder on a fitting You can also judge pressure just by how far fuel squirts out of 1⁄8" hole duh. This is the best way to check the capacity of your system as well.. This way Should measure About a pint a minute, you will have to figure out what just what you need, A low compression 454 is gonna suck the fuel. . Note this,, Whenever you put a thermostat In an engine you must buy the type that when it breaks it breaks= OPEN ! not closed .. This may a count for 10, 20% of the engine Overheat disasters

 

Temp Sensor. If you referring to the two wire sensor next to the thermostat housing, I replaced that last week. The truck would not start but was dumping lots of fuel into the TB. I replaced that sensor and have not had any problems for the last 100ish miles. Until today of course. It was running great. Lots of power, smooth, no missing. It was great while it lasted. I can check the new one though, just to be sure. I am pretty rural so I will need to drive into town and see if any of the parts places have a fuel pressure test unit to rent. Or, I can just buy the adapter and gauge. One way or another I can get it checked. It just will be a few days. That would be checking the pressure before it hits the TBI though, correct?

 

Yes, before the TBI. If I recall correctly, there’s a bolt on the back of the block that holds the fuel lines. If you try to insert the pressure adapter at the throttle body, you’ll have to loosen that clamp to get the adapter on.

 

Both of the fuel lines have been replaced with steel woven lines and are loose enough to fit the adapter in there. I looked up what one looks like and I do have enough slack to get it in there.

 

That will make it easier to get to.

 

So, I got lucky and a buddy had a temporary inline fuel pressure gauge setup. The fuel pressure is running right about 11psi.

 

Pressure problem , Far as I know all TBI should be should have 1,2 to 15 ahead of the internal Fuel pressure regulator You probably rebuilt it wrong actually there's a kit on the market that I alowe you adjust the TBI fuel pressure from inside the body but you don't need that. . Be sure and put in a new Style diaphragm For the fuel pressure regulator this 1 resist s alcohol.

 

Ok, does it fluctuate when you accelerate?

Also, take a strong flashlight and shine it into the throttle body while it’s running. You should see a fine mist cone. There should never be large droplets. At idle and then open it up a bit, say half throttle or a bit wider and see if it changes.

 

(Today) Keeping it running long enough to check is the problem. Last week I did check the injector pattern, after the TBI rebuild, and it had a very nice cone pattern but now I can't keep it running long enough to check, even with a partner to watch. I mean, you can see its initial spray (which looks okay) but nothing consistent. Yesterday I could get it to stay running with lots of throttle (it didn't sound happy but I could keep it running). Today, it tries to start (has spark) but will not stay running for more than a second or two, with throttle or without. With no throttle, it won't start period. It got down to -12 last night so that didn't help anything. It is very sluggish today. Sorry, not a very good answer.

Oh and no the fuel pressure didn't really fluctuate so much as it tremored but there was no heavy movement up or down from 11psi. You could see the pump prime then I watched as the engine ran (with throttle). The tremors were probably more engine vibration effects on the needle than anything else.

 

It's best to use some high pressure line to take out pulses, If you're using some kind of after market pump The stock rotary pump will not have pulses.. Do not run less than £12 or more than £14 at the TBI inlet. Again you better rebuild that TBI and make sure you have plenty of filter right before that TBI. Over 10 microns is too big , this wears out you're injectors. Sounds like they may be clogged up right now. Like the other man said you need a nice spray pattern all the way all the time. Use the camera use the mirror You gonna watch it. And you better rebuild that TBI too. Don't try to. Pusy out Because the little cold I work in northern Minnesota and Canada At 50 below.

 

Ive got a propane heat blower under the truck. Hopefully this will help it to at least run with throttle and help me figure this out.

 

Okay, it is up to 6* outside but more importantly the propane blower under the truck for an hour let me get it running enough to limp, stall, limp stall, etc into the garage. What a pain.

I disconnected the Idle control solenoid, started the truck, ran the engine at around 1200 rpm for about 2 minutes, and it actually idled at a low rpm with no input from me until the engine warmed up to operating temp then it would no longer idle without surging or throttle input. Never did it idle in gear.

However, once it started to not idle at all, I was able to get it to stay running, with a board on the accelerator (so I could watch the injector spray pattern), between 1100 and 1500 rpms. At those rpms it ran and sounded pretty good. Not great but it was almost normal. I let it run like that for about 5 minutes and it stayed running without any additional input from me. Anything below that range of rpms and it would surge, fall, surge, fall, stutter and die. If I put it in gear without high rpms, it would die. Even at high rpms it would not drive well and the moment you put the brakes on to stop, it would die.

When I had it running with the board on the accelerator, I looked at the injector pattern and it was cone shaped without any droplets I could see. However, there was fuel getting splashed back up on the throttle body enough to look wet. I am saying it got wet around the flat areas where the TB bolts to the intake manifold. It didn't drip off to the outside of the TB but it was wet with fuel. Not sure if that is normal. This was when I had it idling at 1000 to 1500 rpm.

Hopefully, all that will help us go further ahead. Thank you much for the help so far.

 

A WAG - your O2 sensor may be bad. It sounds like you have your issue when it goes into Closed Loop.

 

could you explain, closed loop?

 

The computer system in the OBD1 setup has a baseline program (fuel map) that is used to start the engine and get it to operating temp. It is regulated by the coolant temp sensor. Engine Idle sis controlled by the idle air control. That is open loop.

Once operating temp is reached, the computer starts using the O2 sensor coupled with the CTS, knock sensor, vehicle speed, and throttle position to adjust the fuel mixture and timing. That is closed loop. the fact that it seems to run way worse when it warms is the reason we’re suggesting checking the O2 sensor.

 

So, because it idled regularly with the IAC unplugged and I just replaced the CTS, then when the engine warmed up and started acting up, it could be the O2 sensor. Makes sense. What about the throttle position sensor? Based on the flow you described, it could be the problem as well? What makes you say O2? I am trying to understand the process, not second guess anything. It makes sense I just thought about the TPS and it could part of the problem as well. Correct?

 

TPS is almost never the problem. They can go bad, but they’re typically very reliable. I did have one fail and I replaced it and the new out of the box one was bad. Left me with idle stuck at 1800rpm. I left it as I was driving back to Portland in the late evening and didn’t care since I was on the freeway. New one the next morning.

They never throw a code until they’re almost dead.

O2 is possible because we’re assuming the temp sensor is good. It also could be bad out of the box.

Have you had a chance to put an ohmmeter on the CTS to make sure it’s changing?

 

No, I still need to do a resistance check on the sensor. If I can't get the truck running good enough to warm up (iffy right now) I will pull the sensor and use cold and then Hot water and provide the readings. Tomorrow.

I am also going to take a look at the O2 sensor and see if it looks like it was changed with the PO swapping the engine. He left a LOT of stuff unhooked or left old stuff that was in the engine already in place. The distributor was all rusty inside. The cap had a build up of corrosion on the firing contacts worse than any I had ever seen. That was why I replaced the distributor, cap, rotor and coil. It was all suspect due to the shape it was in. Made me feel better anyway. Once I bought the vehicle and transported back home, he never answered any questions I had asked via messenger so I have no background info other than he changed the engine out at some point and never fully finished the process. It ran, drove but lots of things were not working. No gauges at all, lots of wiring just hanging around, etc. It has been a learning process for me.

 

Well, I tried to get the O2 sensor out and it is hidden above the oil filter and below all the engine smog rails on the exhaust manifold. What a perfect spot! Long story short, I decided to pull the engine and do a rebuild/upgrade on the 454. I am just finding so many bad/melted/stripped wires, stripped bolts, etc, that I just decided to pull it and make a huge mess. I really didn't want to do this, right now, meaning winter. My garage isn't big so I need to pull the engine and then push the truck outside to keep the garage warm. Just NOT when I wanted to mess with it but it is what it is.

The final straw was when I pulled the brand new spark wires off the plugs and the boots were already melting. One was melted through. The wires were only on the truck about 100 miles. I never once saw the temp get above 210*. I just don't understand. So, out comes the engine.

Other than the obvious, the exhaust manifolds got VERY hot, what might have caused the exhaust to get so hot to start melting the boots but the engine temp never got above 210*?

 

the exhaust manifolds got VERY hot, what might have caused the exhaust to get so hot to start melting the boots but the engine temp never got above 210*?

Running too lean AFR can overheat the exhaust.

 

The 454s exhaust runs hot; but a little bit off in timing will run hotter than it should

 

New day, new outlook. I was I little upset over the boots melting and the wiring I found all messed up and made a snap decision to pull the engine. Nope, not going to do that just yet. After some thought, I am still going to pull all the smog stuff because the smog system is a total mess. To many parts are broken and just taped together. My state does not do any kind of inspections and I don't know enough to cobble it back together. I will leave the egr part but everything else will go.

I do not think I had any leaks around the TBI area. I just rebuilt the TBI and installed all new gaskets. The TBI mechanicals were nice and snug, nothing seemed worn out. I cleaned the balancer, made a white mark where the timing line is and ensured I had set the timing at, in the end, 5* BTDC. The single wire near the passenger rear of the engine was disconnected when I set the timing and reconnected after. All the vacuum lines were connected and snug, not just barely hanging on. I did need to fix a few as they were cracked and no longer flexible.

When I bought the vehicle, the boots were melted and the exhaust smelled like fuel. I did a bunch of fixes (see the first post) and thought I had fixed that issue. Guess not. While it seems to be running lean, I can still smell a lot of fuel in the exhaust at startup. Quite a bit. Maybe it is only running lean when driving?

I am not sure why it would be running lean. Maybe the timing marks are not lined up where they should be? Would a bad O2 sensor cause this issue? I was getting ready to replace it anyway as suggested by Cowboy and Playwithtbi. Should I set the timing further back? If I go forward much at all it will not run good.

Thanks again everyone.

 

It's usually an air leak.

 

Or low fuel pressure.

 

Okay, i need to check air leaks better or something. Fuel pressure was fine. I ordered a vacuum tester and a fuel pressure tester of my own. I don't think my buddies was bad but you never know. I like having the tools and the tester didn't cost much. I will let you know what I find when I get them and after I am done with removing the smog stuff. Thanks.

 

I have 88 5l and the distributor used to come loose and have you tried to study it by hand and see if it moves , I removed the fork at the base with hold down bolt and bent it so it would secure in place. Just another item to check.