Ok. Lately my truck has been running a little rough when I first start it up... misses a bit until it gets warmed up.

Anyway, today at lunch I went to start it up, and it wouldn't fire. I tried probably a dozen times where it would just cough once, then die. The last time I turned the key, it fired right up and ran quite rough until it got warm. I went to turn onto the highway, and as I went through the intersection, it felt like it was going to stall altogether, but it came back so I turned around and went to the gas station, filled up to make sure I wasn't just out of gas. Filled it right up and went for lunch.

Just now, at the end of the day, the same thing happened again! Once cough, then die.

Now the truck seems to run better warmed up and runs very smooth, but when I let it sit for a few hours, I have problems (engine cold)

The ignition, wires, plugs, cap,rotor are all 6000Miles new. The air filter is clean, and there is gas (at least in the tank)

It runs fine warm, but rough and no starts when cold.. so it makes me think there is something mechanically wrong - as opposed to electrical; ie fuel pump?

Any suggestions?


89 GMC Jimmy, 6000 miles on rebuilt motor.

Thanks!!

 

how do you like that cam in that truck..belive your drivetrain is exactly like mine..was chip added since rebuild??..have a 91 and am shopin for ideas...

 

It's a noticeable improvement over stock. I believe I actually lost a little bottom end and gained a fair amount of mid-end. It's really hard to say using a stock chip and exhaust system. Barring any major setbacks (read wife buying more furniture), I'll be throwing on some Hooker headers into a x-pipe and straight through 2.5" duals out the back. We did a fair amount of work getting more air in, but did nothing to get the increased volume out, so I'm hoping this will help unlease the beast. Even a 1400 rpm(approx. double stock) stall converter would probably make a pretty big difference in off the line performance.


On a scale of 1-10 on a completely stock motor and setup, I would give that cam a 6.5 - I'm a little disappointed by it... but my opinion may change when the exhaust is done.


Many people have told me I shouldn't be using a stock chip, even though compcams says it'll work (and it does work, but I think there is a huge amount more potential)... which frustrates me a little bit - if I planned on chipping it out, I would have picked a higher lift and duration cam to begin with.

I raced a 2002 4wd shortbox, single cab chev with the 5.3L Vortec, hyperteched, and intaked, 3.73s on 33" tires; we were neck and neck up to about 85MPH when he started moving away from me and that made me pretty happy... having a 500lb weight disadvantage, 130K on the tranny, less gear than him...

My quasi realistic dream motor would have been:
383 stroker, SCAT crank
forged everything
ported vortecs with good springs
nice performer RPM intake
thorley headers
~270 duration and .480 lift cam
edelbrock mpfi or accel dfi


If I had the chance to do it all over.. I would seriously consider edelbrock's performer packages, heads, cam, and intake because they give you the chip to make all of that run properly. It's a tested formula, so there is less screwing around with custom chips and parts that might not compliment each others strong points.



Aside from that though.... I threw some fuel injector cleaner in the tank this morning and am changing spark plugs, fuel filter, and cleaning the IAC valve tonight.


Cross your fingers.

 

l would definitley look into haveing a chip made for your truck from everything lve read so far...will definitley get the most out of your cam that way esepeasialy...so far haveing my block done 30 over and decked..stock crank will go back in and rods..will upgrade pistions...turns out l may have lucked out with my donor engine from my old 88 4x4..turns out the heads are iron 64 cc with 194&150 intakes...14101083..aparently part of a crate engine from 88 or 87 ....there also roller rocker heads...just have to put the parts on it ect...may be in luck where block is concerned..will find out this weekend when l pull the puppy..may be a complete roller block less trinkets....lookin forward to it..have been thinkin about your prob where sometimes you can git to 6 k and others you cant...were the good 6k runs durrin cold weather..or crisp..first thing in the mornin sorta deal?

 

6K runs? Not too sure what you're talking about there. The motor has about 6000Miles (10 000KM) on it since rebuild.

Yesterday morning I dumped in a two big shots of fuel injector cleaner, into the tank and I've now had 3 cold starts without even a hiccup. The idle has smoothed out too, so I'm HOPING that the problem is solved. I would imagine that new injectors are in order, but they are way more expensive that I originally thought. As extra insurance, I also cleaned out the throttle body and IAC with intake cleaner ,changed out the fuel filter, and adjusted ignition timing to about 4* (I think I might have to turn it back more - high rpm pinging)


Roller cam motors sure are nice. My guess though, is that unless donor vehicle was chipped, it'll likely be a flat tappet hydraulic...


CanCritter, where you from?

 

Calgary as of this moment but have lived all over western canada and just got back frm 16 mnths in south Cali...was a little to hot for me..can ya belive it..lol...just got back from tryin to get No's of donor engine but its still in old truck ..dont wana pull it till l figure out what lm gona do yet..so many questions...srry not a expert but have a talented touch where machinerys concerned...k was wondering about chiped?..this in regards to electrical or a process to modify heads for rollers.....had a quick boo at engine and was able to see through head ..lifters look to be hydraulic from what l can see....have been looking for the roller set up for this motor but factory gm is pretty expencive..belive the hydraulic or solid roller lifters willl run about $5oo-600 alone...and am not shure what l'll have to do to heads as of yet...there rebuilt so in fine condition and springs are inner and outer spring set up so am thinking these may be right rpm springs...funny thing is was fella that l was thinkin about have do the bottom end for me..local head shop..asked him about the heads and he said theyd be 74 cc chamber heads yet no.s at all sites comee up as 64cc chambers 1.90 1.50....anyway am thinking l should look elsewhere if hes not knowalgeable about these heads..anyway will give him a call this week and see what he has to say ...was wonderin whats the diffrence between a hydraulic and a solid roller set up..is the solid quicker..ie beter responce...and the diffrnce a 1.6 and 1.5 roller rocker arm be...srry to bug ya boss...tryin to gather all this info and sort it out....anyway have some part No.s offa old truck re ecu ect so diein to find out what they are ect...also lve heard somewhere that that carb cleaner may cause havoc with the electrical sensors ect on the tb so ya might wana get to crazy like we would on old gas carbs...what do the injectors for that run$ about and can the stock injectors be upsized with same tb?

 

I don't know much about cylinder head castings unfortunately. Everybody raves about Vortecs though, but then you need an expensive intake.

Solid versus hydraulic roller... My understanding is solid is more reliable in high rpm situations since they don't "pump up" with oil and cause the valves to float. If you're looking at a truck, unless you're drag racing it, I wouldn't bother with mechanical lifters - supposedly a real pain to keep tuned properly. Roller is really nice too, but man, that's an expensive rebuild.

1.5 or 1.6 is the rocker arm ratio. Multiply the lift of the cam by the rocker arm ratio. 1.6 means the valves open more and for longer than the 1.5 ratio arms = more air and less vacuum. Apparently there is great debate about how the industry measures this number.

I used intake cleaner on the IAC and tbi... It works great and it specifically made for them.

Lastly, canadian tire wanted $190 per injector. I think you can get cop car injectors which are direct drop in and rated for higher volume.

 

check if the coolent temp sensor be the waterneck is pluged in and working properly. if its not it could be getting flooded out.

 

up sorry didnt read the whole post. i guess you got things figured

 

Well... I guess my problem isn't solved. I had a hard time starting it again yesterday, and at lunch, it just barely turned over and suddenly there was blue smoke coming out of the throttle body.

I took it in to the engine rebuilder; he did a few quick tests and couldn't find anything mechanically wrong with the engine.

Last night I changed all of the plugs and the cap and the rotor.

This morning, once it was warmed up, I tried to gun it at a stop light and the engine bogged right down and almost stalled in the intersection - but when I let up on the gas, it picked back up and started running again normally.

Symptoms:
Hard starting after truck has been sitting for 4+ hours
Rough low rpm idle and low rpm driving
Truck stuttering and almost stalling when giving it more than light throttle from stop (happened twice)
Sometimes (more noticeable in winter) the engine will idle high then low, then high then low, etc. It almost stalls when it hits the low then revs up and seems to go too high so it lets off, but too much...


Aside from that it, runs great. Lots of power, normally good throttle response. Cruises nice down the highway, not overheating (temperature within normal range).

Things I have done so far:
Changed Cap and Rotor
Changed Spark Plugs (old plugs were good)
Changed Fuel Filter
Added fuel injector cleaner to the tank
Made sure there is lots of gas in the tank
Used intake/tb cleaner to clean out the throttle body
Adjusted timing to about 1* BDTC with est wire unplugged
Checked for trouble codes - none except EGR which is typical
Looked at the spray pattern of injectors at idle.. looked good
I think iginition is good based on the condition of the old plugs


I'm not sure if this makes any difference, but I'm running heavy 20w/50 oil so that my oil pressure doesn't drop so much when it gets hot. I removed the factory engine oil cooler (leaking) last year when I rebuilt the motor

Help!

 

Time for chip burning.

 

I'd like for it to be reliable before putting the time and money into a chip. It's run great for the last 10 months, but in the last few weeks it's really gone downhill with this starting and idling problem. I find it hard to believe that I would _suddenly_ need a chip. Don't get me wrong, I really do want to custom chip the truck, but I need a reliable baseline first.

 

I didn't relaize it had run good previously. I am glad you are aware of the chip thing though. Anywhoo, what is your feed line fuel pressure?

 

I've never tested fuel pressure... What is the recommended way to go about doing this?

I've been driving it around and doing some half to WOT runs with it and no problems - wouldn't a Fuel pressure problem be apparent at half and WOT?

 

Just a thought...Now I know you stated that you have alot of work in the ignition area, but did you change the module? It is one of those parts that can cause alot of mayhem like you are stating. The pickup can also cause these symptoms.
I might be way off, but when I had my 86, it would start up, run for a while. Then after I shut it off, it would not restart for like an hour or so. Replaced the module (took 10 min), and everything was fine

 

l have a similar prob..mine will idle fine then everyonce annd awhile the idle will drop low to almost stalling..it wont stall but dam near.....anyway to make a long story short bein a county boy and all l like to keep things simple and easy..comon sence sorta deal...anyway have been looking realyyyyyy hard at the thermostat as they call for 195s in these tbi's..thats just way to hot as far as lm concerned,,,realy for me thats a high heat thermo for winter as far as lm concerned..dang engine is way to hot in my opinion and after countless hrs of readin have come to the conclusion the 195 thermo was a solution to a desighn prob they had with tbi's that being the intake...l think they found out the intake wasnt as good as they thought it was re it wasnt warm enough for the fuel air mixture so they used the 195 thermo as a quick easy fix for a silly desighn flaw...the 195 made it hot enough for the intake to work as it should but as a downfall would be hard on a engine in the longrun....well this isnt a dwnfall for GM as these engines are gona wear out quicker and there gona need parts..a win win deal for GM..go figure..so will be putting in a cooler thermostat in my engine when l install it next mnth and l bet ya it runs much better....l will have a spare tbi intake so will do useual mods to it and add some sort of controled heat to the intake and be able to regulate the temp in there for a more eficiant mixture summer and winter while running the engine cooler..mayby a 180 for summer and 192 for winter type idea....being yer in Lethbride it should be warming up pretty good down there now and would be a good time to check this out as the hot days will be good for intake while running a cooler engine...it kinda take that and the fact that when l first start my truck on cool or brisk mornings the truck realy likes to get up and go but once its warmed up it seems to die a tad...anyway just food fer thought...

Quick question....wonder if anyone can awnser this...

On the tbi swirl heads the swirls go in opposite directions in the chambers..ie one chamber intake side would be clockwise and the chamber beside it would have the intake going anticlockwise..why?
you figure the swirled would both go clockwise being were in the northern hemisphere....ie...toilets flush clockwise above equator and anti clockwise below the equator...so the swirls that would be working anticlockwise would infact be working against the laws of nature and be a faulty desighn....any thoughts?

To me the tbi set up is a great set up but belive they realy screwed up putting it all together to work in unison....anyway gona do my best to set this puppy up right.....

 

I haven't done the module yet... I was hoping to save up a bit and buy accel 300+ ignition/coil/module as a kit and save a little money. I sure hate to just throw money at a problem like this.

This probably isn't true, but I'd always heard that modules either work and the vehicles starts and runs every time, or they don't work and you vehicle won't start at all.

 

That's not always true of the module. The module is suseptable to high temps, and if the di-electric grease isn't put on a new one, they can fail very quickly because of that. Also the wires going into the module have a tendancy to fail. That is usually when you have a complete 'no-start' situation.
Pickups are a different story altogether. I've never personally had one go bad on me, but from what i've heard, they either work, or don't.
And I didn't know anyone made an aftermarket module (ESC) for our cars(?) I do know that they make them for in-cap HEI, but never heard of them for external coil (or divorced HEI).
Contrary to popular belief, your stock ignition system should be just fine, unless you are running some pretty healthy mods/CR.

 

I have to second jconrad's remarks. I've had modules that would appear to work/not work randomly. But, after taking a closer look, it was probably related to heat. It's definately something to consider.

 

I will definitely take that into consideration. I changed out the Coolant Temp Sensor ($8 - couldn't say no) last night and put a few dollars of 91 oct in the tank. No noticeable difference today (it started fine both times) but my problem seems to be streaky.

I know proform makes an ignition module that is quite popular because it looks completely stock.

Do a keyword search on Summit for "ignition module" and you'll definitely find a bunch for HEI remote coil.


What would you consider healthy mods?

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