Tonight I was driving home on the freeway and, as usual, I had to drop it into drive on occasion get up to my desired speed. We won't mention any specifics here Except for merging onto the freeway, I don't remember revving higher than 4000 rpm's, although it seems I've been doing a lot of driving in the 3500-4000 rpm range on the freeway lately. My new intake manifold has killed most of my low, usable power and if I hit any kind of wind or a grade, I've got go into drive (it really bites!).

Any ways, I'll get to the point here. I didn't notice anything weird while I was driving on the freeway, but when I pulled off and came to a stop on the off-ramp, by idle was extremely jumpy. It would fluctuate between 600 and 900 rpm's very rapidly. Then, when the light turned green my engine was very rough going through 1500 rpm's. Above 2000 rpm's I didn't notice anything weird, but as I had to come to a stop a few more times, my engine would vibrate pretty violently again. Maybe a motor mount or something? I don't know. There was no smoke coming from the engine, none of my guages indicated anything was wrong (ie, no check engine light, my water temp, oil pressure were all normal). I'm going to look around tomorrow when there is light, but I didn't here anything hissing or leaking. This is very strange for me, since I've never seen anything like this. If anyone has any ideas on what they think the problem could be, I'd love to hear it! Thanks.

 

Did you hold it at WOT for an extended period of time (say greater than ~ 4 seconds) w/o an accompanying climb in the revs? If I do that for a long period of time it fouls the plugs. It happens to me when I'm climbing a grade in 5th gear at 75mph w/ the trailer in tow and the cruise on and the cruise sends the pedal to the floor trying to maintain the speed and it doesn't climb but the truck sits at WOT for a 5 seconds or so, it will foul my plugs and run rough for a few minutes. Did it clear up after a time? If these are your symptoms you have two solutions:

- make more HP so that the revs can climb and the engine uses the extra fuel

- back off the gas if its not accelerating..

On a seperate note I have the same intake w/ stock heads lightly ported and a custom cam and love the combo. I don't think I lost any torque except below 1500rpm. With a 4:10 gear you either have tall tires or that thing is constantly in the zone. For me I found that the factory computer is having a hard time dealing w/ the cam (its on a 110 lobe center which makes it more difficult). I have a Pro-M Mass Air Meter and Optimizer combo which SUCKS to tune but the more I play with it the closer I get. In other words, I have found probably 10hp and 10ft/lbs of torque just in tuning it (adding more fuel at idle and who knows what up top)..

What are your cam specs and your computer (Speed Density or Mass-Air).. how about your MAM size and TB size? Just curious.

Jerry

 

Check your vacuum lines also....when one of mine get a leak the truck runs crapy at low rev but ones I getinto 3-4 gear it runs normal.

 

As a matter of fact, I did hold WOT for at least 4 seconds, probably on several occasions. This isn't the first time I've had to do that, but this is the first time I've noticed my truck starting to run kinda rough.

I haven't started my truck since I got home last night. I took the bus to school today so I don't know how it's running now. But I will agree that I wish I had more power. Sometimes, I can hardly keep 65mph anymore in OD. It's an absolute shame considering all the mods. I have. But when it drops down into Drive, my speed climbs up to about 90, so I put it back into OD, and my speed steadily declines back down to 65 again before my tranny kicks back into Drive. This cycle gets EXTREMELY irritating!!! Sometimes I'll get so pissed off that I'll floor it for an extended length of time (ie 5-10 seconds) until my needle climbs up to about 80-85(which means I'm doing around 95-105). I have no complaints about my intake manifold around town or at WOT, but at cruising rpm's (1800-2500) it absolutely sucks, particularly in OD on the freeway. I put my stock TB back in, and I'm not sure what the exact specs. on my cam are. I have the spec. card somewhere in my truck.

So if it is the case that my plugs are fouled, how do I "unfoul" the plugs? Do I drive around for a while, do I flush anything? Perhaps after this, I'll have to swallow my pride and stick to the slow lane when driving on the freeway :o I've always been a fast lane driver and never had any problems keeping 80 in OD with my stock intake manifold. But until I get some more reliable hp, I'll have to take it easy on my truck

Thanks for the suggestions!

 

On my dirtbike(2 cycle engine) when the plug(s) get fouled I replace it.

 

GENERALLY speaking if plugs are slightly fouled on a modern fuel injected/modern ignition car it will clean them up if the original problem has been addressed. When I fouled mine out in my truck it took about 10 miles of driving freeway speeds to clean them. If they are fouled bad, yes you have to replace them.

You definetly have some other problems though. Make sure the plugs are clean and try again and stop holding it a WOT for long periods unless there is an appreciable increase in MPH. I know on my truck 70-75mph in 5th/OD is a dog. I can accelerate harder in 5th at 85mph then 75mph.. go figure. Its just too low in the torque band for the engine to overcome the rolling and wind resistance. Let me know what your cam specs are and what heads your using. My Ebock intake is definetly no slouch below 2500RPM but again I have a different cam.

Is your truck mass-air or speed density. How much timing are you running? You may be in need of a custom chip, ideally burned from a dyno session..

 

To answer a few questions, I have Speed Density, and I have totally stock heads. I do plan on getting a pair of Edelbrock Performer aluminum heads in a couple years though when I graduate college. Have you spoke with dvldog458? I have the same camshaft that he has in his truck. So I don't know if that helps or not.

I fired up my truck again tonight. I didn't take it for a spin yet, but I did notice that the zip tie holding the hose running from my radiator to... I don't know exactly where... the engine was broken. But it didn't appear to have any negative effects. But is there any way I could have broken an engine mount or something? My engine and everything connected to it (ie my exhaust, intake manifold, wires, hoses, headers, etc.) shake pretty good. Would fouled plugs cause the entire engine to vibrate at idle?

I wouldn't think it would be the vacuum lines. I know having leaky vacuum lines can screw up your idle, but I wouldn't think it would cause your engine to jerk up and down. I might be wrong, though. I know it's hard to diagnose a problem on a bulletin board, but I thought maybe somebody had come across a problem similar to this.

I wish I had more time to turn a wrench on my rig, but I hardly even have enough time to bring my truck to a shop. It's pretty pathetic, I know, but we all have our priorities.

Well, I'll be sure to keep you guys posted when I figure it out, whenever that will be.

 

fouled plugs can give you the "jackhammer" effect . loads up and runs bad . but what you are describing sounds like when i had my harmonic balancer crack and rotate 90° on my stang . when i started it up the whole dam front end of the car shook bad . fenders viberated , motor jumped around as if it had a broken motor mount , i suggest pulling a few plugs and inspecting them first . then check the timing . also get a can of wd 40 or starter fluid and spray around the intake/vacuum lines and check for leaks .

 

If I recall you recently added the intake and cam? Or was it just the intake? Speed Density fuel injection systems do not like cams that differ in duration than stock. Without a custom chip or a mass-air convresion, your bound to have driveability problems, very possibly like loading up on fuel which is what you seem to be describing. Dig up the cam specs and let me know. Have you thought about getting a mass-air conversion or going the low-buck route like others on here have described?

Jerry

 

I think I will check the plugs. It's mostly just everything connected to the engine that's shaking. Although I definately won't rule out something like a harmonic balancer crack.

As far as the cam, I think it's fine. I actually had the cam put in in Aug. of 2000 when I had my engine swapped. It's a relatively mild cam, since it's made for fuel injected, computer controlled engines, hence the name Compucam.

I don't know if there is anything wrong the driveability of my truck. I think what happened is that with my 35" tires, my power is a tad low @ 2000 rpm's. Being that I drive my truck pretty hard all the time, and Sunday night I was very hard on my truck, I think I probably cracked something or fouled up the plugs. Once I fix the problem the solution will be to go easier on my truck for one thing, and when my budget permits, beef up the engine some more.

I keep forgetting to get the cam specs, but I'm sure they aren't anything too radical. It's a pretty driveable camshaft.

Thanks again for your suggestions. I have a feeling it could be one of the things you all mentioned. So like I said before, when I get some time I'll let you know what happened.