Hey guys,
I have a AMC 258 inline six in my jeep, with a retrofitted gm tbi setup.
Last summer i got he tuning down and it runs great when warmed up, but when the engine is below 40-30 digrees it runs rough and miss and is undrivable till the it warms up for a few minutes.
How do you guys tune for cold starts?
I have tried leaning out and riching the AFR vs. coolant temp table with little no emprovement. What other factors come into play during warmup.
4.3 tbi
7747 ecu
crag moates burn 1 and eprom
thanks
andrew

 

I almost deleted your post just based on the subject line. You have to remember that this is a 3rd gen f-body site and word the subject line taking that into consideration.

However, GM did use the TBI setups on 3rd gens. Although not on a straight six. Haven't seen a inline six in a f-body since the first gens. Although you could get an straight 4 in a 3rd gen.

Anyway, most likely it is the length of the runners on the intake. Short for the center ones and long for the outers. The outers are the issue. Make sure that the exhaust heat system is working correctly. Other then that more fuel and possibly more spark.

RBob.

 

Andrew/Bob...

I might be running rich! Does the engine bog and miss, or do you have occasional "popback" in the intake when cold?

If it bogs and smells in the exhaust like rich, pull the plugs cold and look at them for carbon and wetness on them. That would be rich then and show rich flameout to cause the miss.

If it pops-back, then the plug(s) would not have the wetness, and that would be lean.

There are some tables for AE for delta-MAP and also delta-TPS versus coolant temp that would be the best place to adjust for the colder (and open-loop) operation, but you need to know which way to tune first.

Also, try a slow increase in RPM (TPS moves, MAP stays pretty constant as much as possible and see if it still bogs. If not, then it would be the delta-MAP table that would need work.

A wide-band O2 sensor will REALLY help you here, as you can then see what the A/F excursion are.

One other thing. The 4.3s had deliberately mismatched injectors side-to-side. you might also have an issue there......

Bottom line is, keep trying, but also try and get a good information feedback from the tune as you can to assist you.

I will end by putting in a plug for RBob's 747-series EFI conversion (sorry Bob, but I need to mention this....). It is a great improvement over both the original code and HW, giving you high-speed ALDL-type output off his Lockers board which the old low-baud 747 just won't do. I think it might be well worthwhile to at least get his base conversion (still uses EPROM), but the new flash version I can see is much better, and might be worth it even though you already have some HW, as it gives you real-time update of the calibration.....

 

Thanks for the help, when i started it up it was definitely rich, it smells strongly like gas.
When i did the slow roll on (neutral) with the throttle it was a little lumpy till it got to 2000rpm then it started to misfire. It will do a similar thing wile driving also.

"There are some tables for AE for delta-MAP and also delta-TPS versus coolant temp that would be the best place to adjust for the colder (and open-loop) operation, but you need to know which way to tune first."
I cant seem to find these tables in tuner pro with the $42 xdf file?

Now if im running rich whats a good amount to drop the AFR?

I looked at that setup you described, it definitely looks pretty sweet, i like the MPG readout. but unfortulity i lack the funds for that setup (poor collage student).
thanks,
andrew

Rbob: i tried changing the title of the thread. by all means please change the title to something a little more suitable for this forum, if you want.

 

Might try pulling a plug after running it cold. Could either be too lean or too rich. Too rich will leave lots of soot behind, letting you know that you need to back off the cold enrichment Also, at very low temperatures, fuel is much less volatile, and this leads to fuel puddling and rich/lean spots in the combustion mixture with setups that dont have any form of heating, which from my experience requires a good deal of tuning to find the sweet spot.

 

any luck ever getting your jeep to run better? i've got a similar setup on my 88 YJ (with amc 258 and 4.3 TBI) that i'm about to start trying to tune. ever since i added a Borla Header and HEI ignition it seems to run rough in the mornings until its warmed up. if you havn't figured it out, maybe we can compare data once i'm done logging today

 

Since you menation a header, do you have a heated O2 sensor?

If not, then that is most likely the culprit!

You can wire one in (recommend a 4-wire since you have a header) using a relay off the fuel pump relay, so that it comes on only when the main relay has energized the fuel pump. Use a seperate relay for the O2 sensor so as to not overload the FP relay, and be sure to put a fuse in the power supply line of about 15A.

 

hmm i have a 1 wire o2 sensor on there right now, i'll give the heated o2 sensor a try as soon as i figure out which o2 sensor i should be trying. thanks for the heads up about that, would be great if thats all it is. i'll report back later this week

 

i'm attaching 2 log files i did the other day with winaldl. named accordingly. These logs are just when its idling in park.


anyway, i'm looking into the heated o2 sensor info and i see 4 or 3 wire heated o2 sensors. does it matter which one i try? seems 3 wire are easier to find adapter plugs at local parts stores.
after doing a ton of reading which i plan on continuing doing tomorrow, it makes perfect sense that a heated o2 might do the trick considering my header.
thanks for that tip, even if it doesn't resolve my problem, its def something that i should have. i'll report back after i try it out.

 

After a cold start the engine isn't in closed loop. In this case a heated O2 won't help.

Make sure that there is a method of getting heat into the intake manifold. The GM inline 6-six's had an exhaust heated area right under the carb (TBI here). They also had heat risers off the exhaust manifold providing hot air into the air cleaner.

Note that a rough engine is also a sign of too much spark timing.

RBob.

 

Thanks for the reply RBob, much appreciated.
is this what you mean?
http://img399.imageshack.us/img399/6224/p1010718yd7.jpg
i do have one (the one in the picture was my old one before i pulled another from a Junkyard that was in better condition. (couldn't find a new one)
i'll double check to make sure its getting power and working. its located right below the TBI on the bottom of the intake manifold.

I think my timing is around 8, if i go too much higher it bogs down and back fires under a load. and if i go lower it won't idle even when its warm.
thanks again for the help

 

Which ECM are you using?

Note that there is coolant compensation spark advance. Along with after start SA.

RBob.

 

1227747 is the ecm. It's actually the howell fuel injection kit. It was on the jeep when i bought it. Their kit is basically a modified 4.3 GM TBI which i'm sure you already know.

 

i tested to make sure the manifold heater was getting power today and noticed it wasn't. i hooked it up temp with a switched 12v to see if it made a difference. the jeep still stalled quite a few times. my logs don't apear to be any different, but i'm still learning how to understand the logs to be honest. i'm going to hook up the manifold heater properly later this week when the rain stops since i don't have a garage to work out of.

 

spoke with Troy at Howell and he said i should check my fuel pressure since if i pinch my return line it seems to run better. guess i'll take a look at that if i can find my fuel pressure tester.