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Found 4 results

  1. I have a 1994 Chevy C1500, 5.7L engine. My truck idled high and I finally got around to replacing the idle air control valve. This didn't fix the problem and it continued to idle high. I determined the issue to be a vacuum leak, so I replaced my vacuum hoses and checked connections. I tested by spraying carb cleaner and the engine still bogged down at this so I cleaned the throttle body and made a new gasket for the throttle body because that one was falling apart. After doing this, the truck began idling extremely low. It threw the EGR code, so I have since replaced the EGR valve and EGR solenoid. Neither of these fixed the problem. Next on the list is to replace the throttle body gasket along with the distributor cap and rotor. Additionally, my truck will also struggle to accelerate. The confusing part is this- there seems to be no rhyme or reason as to the low idle. Sometimes, the truck idles in park at 800-900 RPM and is able to adjust the idle to the load of the AC being turned on. Other times, it idles in park at what is most likely 300-400 RPM because it doesn't even register on the gauge. It does not seem to have any consistency as to if the engine is hot or cold- it just seems to be whenever it feels like it. This evening, while working on it, it started straight up once and idled great at 800 or so RPM and handled AC and headlight load. While the AC was running, we unplugged the wire that makes the AC compressor run- this dropped the RPM down to around 700 and it never recovered from that. The truck was turned off and started again. This time it idled around 700. Truck was turned off and started again- this time it idled around 500-600. The truck was turned off and now it had to be given gas to start and idled low, around 400-500. Any ideas to explain what is causing this? We are all going mad trying to troubleshoot this and figure it out. We've checked so many things and nothing seems to be causing the problem. Any help would be greatly appreciated.
  3. Here's a brief summary of the issues I was having with my 04 Suburban 1500 Z71 with L59 5.3L Vortec. I have owned the vehicle for a couple years and always thought there was something "off" about how it idles and performs, especially during the winter. Due to my limited mechanical knowledge up to this point, I didn't think it was a big deal. A couple weeks ago, I decided to buy $30 code reader from Amazon. Within 24 hours, I had many codes pop up, and eventually I found a single issue to fix all of them. Codes included, knock sensor low voltage bank 2, too lean on both both banks (most consistent code, bank 1 and 2 always showed up together). heated O2 sensor resistance 1 bank 1, random misfire (only once or twice), MAF low voltage, and something about the transfer case I think only once. I found a video on youtube after searching "lean on both sides 2004 Suburban" and got basically an exact match for my vehicle and it also had the same problem, which is very common on the Vortec engines...it was a bad intake manifold gasket, and by the looks of it, it was the original (I have 288,000 miles). I'll try to put the pictures in order from the start of the project to the finish. I cleaned up the heads, and valley pan, changed both knock sensors and the harness, bench tested my MAP sensor and all fuel injectors (hooked up to 12v power supply and shot carb cleaner through them), and power washed the intake manifold. I left the factory foam on the intake manifold, but I also used sealant to create open (horse shoe shaped) dams around the knock sensors and a line directly underneath each piece of foam to help complete the seal that should have been there to begin with. Very important: USE FEL-PRO BRAND GASKETS!!! Many people say they don't fit right, but you just have to make sure that the area around the bolts that they hook around is clean so that they can snap all the way on. The alignment may look slighly off, but I think it has something to do with how the cylinders are angled. It took me about 3 days, 4 hours a day from start to finish. When I finished tonight, I primed the fuel lines a few times and checked for leaks, since I removed the rails and injectors because the plastic quick disconnect tools suck. Well, the smaller size worked on the small line, but the bigger one was not thick enough to get the clips to release. I was not prepared for the amount of fuel that would come out and I had a propane heater within 3 feet of the vehicle so BE CAREFUL!! I almost killed myself jumping off the engine and getting my pants caught on the hood latch in order to quickly turn off the heater. Anyway, I only had to turn the key once for 2 seconds and it started right up, then sputtered for about 10 seconds (no accelerator needed), then seemed to flatten out. I could no longer hear a hiss coming from the engine bay and it just sounded "healthier". I took it for a drive and noticed a HUGE performance gain. I have never felt this much power come from this vehicle. I would say before the repair, I was only getting 230hp. Now my guess would be around 285hp. From the factory, the L59 should produce 295hp. After starting the engine and before the drive, I got one misfire cylinder 5 code, but I'm assuming it was probably just an air bubble from the fuel lines since the code did not show up again, nor did any other codes for that matter. I am very happy with how this repair turned out, since the only part I replaced before the intake gasket was the throttle body/IAC assembly, which had a part inside of it rattling around that shouldn't have been, but it hardly made a difference. About six months ago, my mechanical knowledge was limited so an average grasp of vehicle wiring and electronics a and beginner level grasp of engine mechanics. Since then, I've just been Googling and YouTubing like no other. This was by far the most advanced repair I've done to date. Before this, the biggest repair was a battery, alternator, idler pulley, and belt replacement. I finished up by degreasing the most visible parts of the engine to increase the satisfaction I had already gained from this incredibly fun learning experience. Also, thank you to all who have been following my posts and for the helpful responses. I'm sure I will be back soon enough! The other forums are terrible and I found no help on any of them. I have no idea why it won't let me add photos (something about a 4.88mb limit, but my photos are all around 2mb), so I'll attempt to add them in a reply. I hope it's not against the forum rules.
  4. I have a 2004 Suburban that has had a low idle (400 rpm) ever since I bought it. I've also had an intermittent no-start (cranks but won't start) that has been getting worse and worse and usually happens in the winter and it has now begun stalling especially when the engine gets warm. It only stalls when I'm parked. Is there anything that can cause a low idle AND an intermittent no-start? I'll explain the symptoms below. Low idle: If I just tap on the gas, it bumps up to 1000 rpm, then drops off unusually quickly and dips to about 300 rpm before slowly climbing back to 400 rpm, but it never stalls when this happens. If hit the gas and hold it for a few seconds at 2500 rpm or so and let off, it doesn't drop off as fast. The engine slows down at a normal pace until it hits 600 rpm, then slowly decreases to 400 rpm. I'm going to be cleaning the throttle body and MAF sensor today to see if it helps. No-start: It's not the security system, since it doesn't fire at all. With the security system it will run for 3 seconds, then die. I have also checked the fuses and relay. Seems to be completely random, it probably starts 50% of the time. These "episodes" come in periods of one to two weeks, then goes away for months at a time. I think maybe disconnecting the battery or a dead battery is what usually sets it off. When this happens, the fuel pump doesn't prime and if I jump numbers 30 to 87 of the fuel pump relay, the fuel pump runs constantly and I am able to start and drive no problem. Using a multimeter, I was able to conclude that there is no ground control signal going to the relay from the PCM. The fuel pump draws about 7 amps, which to me, sounds pretty normal. Aftermarket items include 3 amplifiers for 4 subwoofers and 4 door speakers, Blade_Al with Drone Mobile auto-start, and a newly installed capacitor. I have recently replaced the battery, since the old one froze and wouldn't hold a charge and I believe it froze because the alternator was not charging properly due to worn bearings. I also upgraded the charging system wiring to 2 gauge to accommodate my sound system. Last night I got it started and began tugging on every bundle of wires I could possibly find (took 45 mins), paying special attention to wires leading to the PCM and the wires under the steering column and it made no difference in how the engine was running. The only thing that changed anything is that unplugging the MAF sensor increased the idle to a normal rate. Plugging it back in made no difference until the next time I started the vehicle...then it went back to 400 rpm. Finally, this morning it wouldn't start on the first attempt so I turned the key to "off" and waited 10 seconds. I turned the key to "on" and the fuel pump primed and I was able to start the car 10 times in a row and drive to the store without it stalling. Since I didn't move anything between these attempts, I don't think it could be loose or broke wiring. Could it be the fuel pump control transistor on the PCM? Transistors are not mechanical, so it would make sense as far as how random this problem actually is. Should it attempt a solder re-flow on the PCM as a last resort? It seems like the warmer weather is helping the no-start to a certain degree, but a warm engine still seems to make it worse. Thanks in advance for the answers!
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